If you have a question for the MXperts, send it to email@example.com
RM250 VERSUS YZ250: DRAG TIMES
My friend and I own a practice track near my home, and within the track
there is a very long straightaway as long if not longer than a football
field. I take the inside line on my 2005 YZ250 in the turn before the
straightaway in second gear and hammer it, then I power shift into third
and it's still pulling super hard before I have to break for the next
corner. Now, my friend who owns a 2004 RM250 says that he is fifth gear
almost maxed out, and he takes the same line as me, my lap time is
faster also. My question is are the gears much taller on the YZ250, and
does the YZ250 have the most top end pull of any other stock 250
2-stroke? because it sure does feel like it.
The YZ250 is geared lower in first, second and third (the Suzuki is
geared taller in fourth and fifth), but the gearing differences will not
make the dramatic gear selection choices that you and your friend are
witnessing. The actual reason is that the Yamaha produces a much longer,
torquier and slower revving powerband. The result is that you can use
each gear on the YZ for a longer time than the snappier, faster revving
and shorter powerband of the RM250. Once the RM250 goes through its rev
range, which is shorter than the YZ's, your friend has to shift or go
For comparison (on a 2004 RM250), the RM makes 46.8 horsepower at 8500
rpm, but by 9000 rpm the RM has lost five horsepower. The YZ250 makes an
identical 46.8 horsepower, but at 8800 rpm and doesn't lose five
horsepower until 9600 rpm. In fact, the YZ is still making more than 45
horsepower at 9100 rpm.
In short, although your YZ250 is geared slightly lower in the first
three gearsthe difference is related to powerband, top-end rev and
duration of rev (the speed at which the bike goes through its powerband
Here are the gear ratios of an RM250 and YZ250 for comparison.
GEAR..... SUZUKI RM250...YAMAHA YZ250
First.........1.800 (27/15)........1.929 (27/14)
Second... 1.470 (25/17)........1.533 (23/15)
Third........1.210 (23/19)........1.278 (23/18)
Fourth......1.000 (21/21)........1.091 (24/22)
Fifth......... 0.869 (20/23)........0.952 (20/21)
AMA NATIONALS: THE TEXAS QUESTION
Will there be a National in Texas in the future?
The AMA has not released the 2007 AMA National schedule, but we expect the Binghamtom, New York, 250f/450 National to be replaced by a new date in the Southern part of the USA. The most likely places are Florida, Texas or Georgia. When you hear rumors that National tracks are going to lose their races and be replaced by an AMA National at Punkin Center Raceway in Podunk City, you can rest assured that is not the case (and if the AMA tried to take a National away from an existing promoter, lawyers would quickly be involved). Every AMA National track has a contract that runs through 2009 at the very least (and some to 2010). Promoters need long-term contracts in order to justify making infrastructure improvements to their tracks...without some contractual security the promoters would have no incentive to spend money on making their facilities more National friendly). Binghamton has a contract also, but Binghamton has the right, under their contract, to sell or move their race to another location. It is assumed, although not 100 percent certain, that Binghamton intends to find a buyer or a partner and move the National to a state that provides the series with better market saturation (since Binghamton and Unadilla are so close together they don't give series sponsors, manufacturers or fans the best overall exposure for the sport). If Binghamton doesn't make the move, the AMA still wants to try to cajole National tracks that are too close to another National to look for alternate facilities in the South. At the very least, by 2010, Texas will have a Nationaland maybe sooner.
WORKS BIKES: HOW LONG DO THEY LAST
Do Ricky, Chad and Bubba use the same bike for a whole season?
No. As a rule, factory riders get a completely new bike every four races.
2006 YZ250: THE PERSISTENT YZ250 PING
My 2006 Yamaha YZ250 has stock jetting, lower gearing and a Pro Circuit pipe, but it pings under a load. What is the solution?
You have two simple solution: (1) Add a small amount of race gas to your pump gas (which you must be running since your YZ250 is pinging). Don't run 100 percent race gas, just add one gallon of VP Racing C12 to four gallons of pump gas. That should fix your pinging problems. (2) Even cheaper, you can change the stock N3EJ needle for N3EW (the N3EW needle is richer on the straight portion of the needle). The N3EW will come stock in the 2007 Yamaha YZ250.
KTM RISING RATE: NEW LINKS
My question is in regards to the KTM rising rate. If I am not mistaken this is arrived at by placing the shock mounts in such a manner as to achieve a rising rate through the change that occurs in the shock/swingarm/frame relationship as the shock travels through its stroke. If this is the case and the bike's suspension reacts poorly to changes (i.e. either too stiff for the small stuff to avoid bottoming, or too soft for big hits to soak up chop) due to its rising rate, couldn't mounts be made to adjust this? Much like several companies do with suspension linkages. I am talking about a bolt-on mount or set of mounts installed in the stock shock mount location machined to reposition the shock mounting location, therefore changing the sides of the isosceles triangle used to create the rising rate. Is this feasible?
Your analysis of KTM's rising rate correct. Several years ago we asked Horst Leitner, who designed the prototype single-shock KTM back in 1989, what it would take to get a better rising rate. He said that KTM's shock location was wrong and that they needed a straighter rate change, but when we asked him if we could make brackets or weld on new mounts, he said that it would require too many modifications to the frame to make it feasible.
Our complaints with KTM's rear suspension has nothing to do with the single-shock, no-link idea. We like it as a concept. It is lighter, easier to work on and, if done properly, would move the shock off to one side of the intake tract for better power. Our problem with KTM is that the rising rate has been wrong for the last eight years, and instead of changing shock location to improve the rate change, they have given us a series of complicated dual-piston shocks that haven't been a solution. Even if the shock was a solution, how long would the damping, shims and oil maintain their perfect settings.
The best suspension system aren't shock dependent, but system dependent. For 2007 KTM has changed the location of the shock. Did they go in the right direction or the wrong direction, that is the question?
2006 CR250F: A QUICK SPEECH & THEN THE ANSWER
I have a 2006 CRF250 and I was just wondering how could I make it go faster without spending heaps of money on it.
A tourist on a New York street stopped a passerby and asked, "How do you get to Carnegie Hall from here?" and the passerby said, "Practice, practice, practice." The moral of that story is that the cheapest way to make your CRF250 go faster is to practice. Faster bikes aren't the elixir that everyone supposes them to be. America's fascination with throwing money at everything, evidenced by the fancy cars, McMansion houses and $150 sunglasses, disguises a puritan weakness that is the bane of modern life. We can't buy coolness, speed, status or position. In the long run, it can only be earned with hard work (20-inch chrome mags don't cut it).
That said, everyone wants to make the most of what they have...and you would not be content if we told you that the best way to make your CRF250 faster, without spending heaps of money on it, was to keep it supplied with fresh oil, new clutch plates on regular intervals, the best tires as possible and to fix ever flaw as soon as it shows up. The best bike for someone on a budget is a well-kept stocker. Now that we've bored you with the truth, here is a list of a few things that you can do to make your CRF250 faster:
(1) The CRF250 gearbox has too large a gap between second and third gear. The stock gearing lays down if you try to short shift. Second is a little too low and third is too high. The best solution is to gear it down with a 52-tooth sprocket (this will make it easier to get to third).
(2) The stock CRF clutch lacks strength. The quick fix? Stiffer clutch springs. You'll think somebody hopped up your bike when you feel the extra bite of stiff clutch springs.
(3) For 2006 Honda mounted a 40mm carb on the CRF250. Most MXA test riders prefer last year's 37mm Keihin FCR because it doesn't bog when you land from jumps, but it is expensive to mount. A cheaper solution is a TBT carb insert insert that sleeves the stock 40mm down to 37. We tried it and we liked it. It costs $79.95 at (509) 941-7716.
(4) Every MXA test rider liked the DR.D single-sided exhaust system. It worked very well, but best of all, it matches your request for mods that don't cost of heap of money. Because it is a single exhaust it cost a couple hundred dollars less than comparable twin-exhausts.
TWO-STROKES NATIONALS: NOT READY YET
Has anyone thought of or will promote Two-Stroke Nationals, like the Four-Stroke Nationals?
Someone does hold a Two-Stroke National (in conjunction with a vintage race), but this idea will need time to catch on. The original Four-Stroke Nationals rose to popularity on a groundswell of nostalgia in the late 70s. It may take a few years before people become nostalgic about bikes that are still available on the showroom floors.
2003 CR250: ROCKY MOUNTAIN HIGH
I recently moved from the Mecca of two-strokes (San Diego, Ca) to Denver, Colorado (military orders). I am having a difficult of a time trying to adjust my fuel/air mix on my 2003 CR250. Do I need to re-jet? The throttle response is very unpredictable, it likes to jolt then go flat. Any insight would be grateful!
As a rule of thumb, you always go leaner as the altitude goes up and as the temperature goes up. That said, the best way to find the perfect jetting for Denver is to find a CR250 rider (from Denver) and copy this jetting. Although we could tell you the basic jetting trends for altitude, it probably wouldn't work all that well with the 2003 CR250 because it is a bear to properly jet at sea level.
Stock 2003 CR250 jetting is a 420 main, 30 pilot and 6BHY38-73 needle (at sea level). To go above 5000 feet, the book suggests two sizes smaller on the main, one size smaller on the pilot and a leaner needle. The fly in the ointment is that at sea level, the stock jetting was too lean down low and too rich on top. So, we ran a 400 main (two sizes smaller), larger main (40 instead of a 30) and a GBHY38-70 needle (instead of the 73).
Without living in Denver we'd think that you'd need at least a 400 or 390 main, although the stock pilot might be okay (which you confirmed by the fact that the bike hits hard down low and then goes flatwhich is probably the overly rich main).
Check with your friendly local dealer.
2003 HONDA CR250 (SEA LEVEL)
2006 KX450F: THE FOOTPEG QUESTION
I have done everything that you guys suggested to my KX450 (linkage, shock settings, ride height, fork offset, gearing, 110 rear tire, etc) and it is twice as good. Is there anything I am missing?
We run KX250F footpeg mounts on our KX450F. They are stronger than the stock KX450 mounts because they are steel. We think the stockers are iffy. The part numbers for the parts we use are p/n # 32054-0021 and 32054-0020. You will also need KX250F footpegs to fit in the mounts (and we recommend getting all new pins and springs).
SOCAL TOURIST: REM QUESTION
My family is coming to Southern California on vacation this summer. I want to come out to Glen Helen and watch an REM race. Where is Glen Helen in relation to my Uncle's house in Temecula, California, and when are the races?
Temecula is about 75 miles south of Glen Helen, which by SoCal standards is considered right next door. To get to Glen Helen from Temecula, take the 15 Freeway north until it joins the 215 Freeway (just before the Cajon Pass), turn South on the 215 and exit at Palm Avenue. Turn left on Palm and follow it over the railroad track and you will see the Glen Helen signs (plus Mt. Saint Helen part of the track is visible to the west). REM races are held on Saturday mornings, not Sunday, and practice starts at 9 am. There are REM races at Glen Helen on August 1, August 19 and August 26. Call (858) 484-1441 for info once you are in California.
MUFFLER: CARBON VERSUS ALUMINUM
I'm trying to choose between a carbon fiber muffler and an aluminum muffler. Which is best?
Given that they both have the same dimensions in terms of length and core size, there will be no performance difference. The two so-called advantages of a carbon fiber canister are; (1) The carbon fiber can be lighter and (2) It looks tricker. If money is no object, go with the carbon fiber. It will cost more initially and wear out much quicker (thus costing more when you have to replace it after about one year of racing). As for the MXA wrecking crew, we would opt for an aluminum or titanium can. They hold up better to normal abuse.
2006 YZ250: RAD VERSUS MOTO TASSINARI
In your suggested mods for the 2006 YZ250 you mention the Rad Valve and the VForce3. I have read your reviews on both products, and you have good things to say about both, but I'm confused as to how they differ from a performance standpoint. I'm curious to know how they compare head-to-head. Are there any defining characteristics, or will I have the same results with either? Does the MXA wrecking crew have a preference?
Both the RAD Valve and Moto Tassinari added to the YZ250 powerband. The Moto Tassinari was a better from low-to-mid (and in the middle), while the RAD valve was better in the midadditionally, with the spacer removed it was possible to increase mid-and-up with the RAD valve (at the cost of the low-end). Test riders liked both reeds better than stockand didn't have a clear preference of one over the other.
2006 YZ250: THREE PC PIPES
I wanted to ask about the Pro Circuit Platinum 2 pipe (Torque Pipe): Is the extra low and mid boost a free gift, or does it lose some top end power vs the stock pipe? Does the power peak sooner requiring you to short-shift more often, or can you still ride the same as you would with the stock pipe?
We have run the Pro Circuit Torque pipe and it does trade top for bottom. Riders who preferred to short shift chose this pipe. The stock pipe has a very nice overall curve, with a little of everything, but not as much of any single trait as the three Pro Circuit pipes we have run on our 2005 YZ250.
(1) The Torque pipe had more grunt, was great on thrust, but signed off sooner and required the rider to shift on the bubble.
(2) The regular Pro Circuit Works pipe gained the most horsepower in the middle and revved out crisply. It gained over two horsepower and tended to push the stock YZ250 jetting to the edge of pinging. But, we could easily fix that with a small amount of race gas or by changing the stock needle for an N3EW needle (it is richer on the straight portion of the needle).
3) The third pipe was Chad Reed's 2005 YZ250 pipe. It was actually more like the torque pipe than the Works pipe...and it wasn't as snappy or powerful as the Works pipe. Why? Reed's engine produced over 50 horsepower and his pipe was designed to meter the power output to his personal tastes. This pipe us not for sale, but you wouldn't want it on a relatively stock engine anyway.
1998 YAMAHA YZ400: EIGHT YEARS AGO
I was wondering if you could send me suspension setup info on the 1998 YZ400F?
Here are the setting we used on our 1998 Yamaha YZ400.
The MXA test crew swapped the stock 0.45 kg/mm fork springs for a stiffer 0.46 kg/mm springs. This helped level out the chassis and was the most significant improvement we could make to the YZ400. Although the front forks look identical to 1998 YZ250 forks--they aren't. In order to handle the extra mass of the YZ400 the fork springs are stiffer, the oil height is lower and the compression damping is stiffer.
Here was our best fork set-up in 1998:
Spring rate...0.46 (0.45 stock)
Compression...8 clicks out
Rebound...11 clicks out
Fork leg height...5mm up
The most significant rear suspension trick that we used in 98 was the set the sag at a rather high 90mm. The 1998 Yamaha YZ400 worked best with less rider sag.
Here are MXA's shock settings from 1998:
Compression...12 clicks out
Rebound...8 clicks out.
Shock Note: The rear shock uses a 5.4 kg/mm (302 lb/in) spring. For the majority of riders this was a good spring rate, but heavier riders will want to switch to a 5.5 or 5.6 kg/mm.
The YZ400 shock linkage has the identical ratio of the 98 YZ250, although the swingarm is a 97 model. Be sure and grease the shock linkage and steering head gearing at regular intervals.
BIKE DESIGN: SX OR MX?
With the popularity of Supercross, when the factories design a bike for production do they design the bike for motocross or Supercross? Would they ever design one for motocross and one for Supercross separately in the future?
The factories design production motorcycles for outdoor motocross. Although there is some consideration given to Supercross, it is very minor...and mostly related to the fact that modern outdoor tracks have some Supercross-type obstacles (whoops, step-up/step-offs and big jumps). The testing starts in Japan about three years before the bike goes on sale and moves to America two years before. The test version is ridden at a wide variety of tracks by a small number of test rider of varying skill levels. A typical weight range is chosen for each engine size (approximately 180 pounds for a 250 two-stroke or 450 four-stroke) and, although the main test riders are very fastthey aim the bike at a rider somewhere between Novice and Intermediate (C and B class).
They will never build a Supercross-only bike for three reasons: (1) A true-to-life Supercross bike is a brutally stiff, virtually unridable machine in anything but Supercross. (2) Most consumers use their bikes on outdoor tracks or local riding areas. (3) Sales numbers aren't so great that the factories can't justify a special version (although the idea of a "special edition" is tried occasionally in very small numbers, but is normally cosmetic).
2001 YZ426F: NUMBERS GAME
Would you guys be able to tell me the base setup on the forks and shock for a 2001 YZ426F. I am a Top Vet B rider.
Here is what we ran in our 2001 YZ426F.
The stock 2001 fork spring was a 0.46kg/mm. If you plan to race the YZ426F with any level of aggression, we recommend going to 0.47kg/mm forks springs (Yamaha part number 5GR-23141-00). Once you have switched to the stiffer spring you can raise or lower the oil height to tune in the exact amount of midstroke and bottoming control you want (a lower oil height will make the fork smoother through the middle, but easier to bottom, while a higher oil higher stiffens both the middle and bottom).
Our best fork settings in 2001 were:
Spring rate: 0.47 kg/mm (0.46 stock)
Oil height: 130mm
Compression...7 clicks out
Rebound: 9 clicks out
Fork leg height: 3mm above top of stanchion
Every test rider liked the rear suspension on the 2001 YZ426F. The rear suspension was well sprung, ably damped and well set-up. The stock spring rate is 5.4kg/mm, which is in the ballpark for almost any size rider.
Our best shock setting in 2001 was:
Spring rate... 5.4 kg/mm
Compression...11 clicks out
Rebound...12 clicks out
SOFTER FORKS: CHEAP AND EASY
I do mostly off-road/hare scramble type of riding. Is there a easy/cheaper way I can mod the standard fork shims to soften up the front end?
The cheapest and best way to soften front forks is to lower the oil height in the forks. The oil height controls the size of the air chamber (which works like an air spring) inside the forks. The higher the oil height the more the resistance ramps up. The lower the oil height (and the larger the air chamber) the less the forks fight travel.
Start by lowering the oil height in each leg by 10mm. At first, don't change the clickersjust the oil height. Then, ride the bike. It will be appreciably softer. But, of course as it gets softer it is more likely to bottom over big jumps. If, when you ride with the lower oil height, it does not bottomyou could lower the oil height another 5mm. If it does bottom, turn the compression clicker in several clicks. Since the compression clicker affects the last few inches of travel more than the first few, you can use it to stop bottoming, without making the first part of the travel stiffer.
The whole process is one of trial and errorbut it is cheap to do.
2004 RM250: DIALING IT IN
I have a 2004 RM250. If my money was your money what would be the first things you would spend your money on for improving the bike?
Here is a list of the things we did to our 2004 RM250:
Gearing: We left it alone it alone. It's perfect.
Fork settings: The stock spring rate was acceptable to most skill levels. We ran the compression on 10 and the rebound on 13.
Shock settings: We loved this shock. Set the low-speed compression on 10, high-speed at 1-3/4 turns out and the rebound on 12.
Jetting: We had to lean the RM250 out by two mainjet sizes. We ran a 162 main, 48 pilot and the optional NEDJ needle (in the second clip from the top).
2000 YZ426F: USE A SHOEHORN
Would a 2000 YZ426F engine fit in a 2006 YZ450F frame and how would you do it?
The answer to your question is no. The 2006 YZ450F engine is totally new from the ground up and the aluminum frame was designed to fit around it. The second answer is that anything is possible with enough money and know-how.
A PERSONAL APOLOGY
I want to publicly apologize to Steve Whitelock and the AMA for my emotionally charged comments published in the June 06 issue of MXA. It was very unprofessional of me to diminish their credibility in the way that I did. My family and I are true fans of RC. The controversy surrounding the fuel rule and the twenty five point deduction caused me to represent comments that I regret. I ask for forgiveness from Steve, the AMA, and the fans. Thanks MXA for allowing me to right a wrong.
We are proud of you. MXA is the AMA's biggest critic. We point out every mistake they make, both in the magazine and in person. But, even though we don't like the way the AMA administers the rules (what rules that actually are enforced), we try not to impugn the men who run the sport at the ground floor. It is a tough job. It is a thankless job. Worst of all, it is political hot potato. Steve Whitelock, as well meaning as he is, is not the AMA. He is just one player in a sport that is controlled from afarby shortsighted people with their own agendas. We talked to Steve and delivered your apology.
For those who don't remember the original letterit follows, along with MXA's answer from the June issue
The AMA has been losing perspective for years. AMA race manager Steve Whitelock doesn't look like he could ride my three-year-olds' tricycle to the mailbox for the morning newspaper. Why don't they hire David Bailey, Hurricane Hannah or Roger DeCoster?
(MXA answer in June issue) Oh yee of little faith. Steve Whitelock was the one of most respected mechanics on the AMA and GP circuit. Steve wrenched for some of the best riders in the sport's history, worked on the FIM jury, ran the Honda GP road racing team and has a world of knowledge about racing. In MXA's opinion he has been handcuffed by the men above him at the AMA. We hope that he will get to make his mark in a positive way in the coming year. Bailey, Hannah and DeCoster don't want the job because if they took it you'd be writing a letter about them next year.
1997 HONDA CR500: THE MAN'S MACHINE
I recently purchased a 1997 CR500 which I am rebuilding. I had a few questions. One, What suspension settings do you recommend? I'm 230 pounds and ride mostly moto (40 Novice). Two, What pipe do you recommend to "soften" the power to where I can hang on to it for 20 minutes? Lastly, are there any other tips you can offer for this bike?
The Honda 1997 CR500 made a lot of power, but it put that power to the ground in such a way that even a Novice could go fast on it. Honda discovered on the CR500 that the easiest way to tune the CR500 powerband was with gearing changes. When test riders requested a smoother power delivery, Honda, rather than changing the cylinder, just raised the gearing one tooth on the rear. This simple fix really works!
If changing the gearing up or down to suit your need for speed is the simplest way to modify the powerband, then getting rid of the stock CR500 mega-silencer is the easiest way to get more power. We replaced the stock silencer, which is really two silencers and a dead air space disguised as a bazooka, with a Pro Circuit silencer. The difference is noticeable everywhere in the powerband; improved throttle response, beefed up the midrange and higher (and harder) rev on top.
Honda has made very few changes to the CR500 from 1992 to 1997, but they did try to update the suspension. Unfortunately, in '96 and '97 they used Kayaba forks. If you plunk around on the CR500 and ride it conservatively, the 97 fork feels pretty plush. That plushness goes away as soon as you turn up the wick. Speed translates into bottoming (not only over big jumps, but also big bumps). The quick fix is to swap the stock 0.42 kg/mm fork springs for stiffer 0.43s and set the compression clicker six clicks out.
In the case of the rear shock, we preferred the 95 CR shock to the 96 or 97 model. The new dual-compression adjuster shock has a harsh, firm and taut feel to it. It was so stiff that it only delivered the sensation of movement over big jumps or big G-outs. Our rear suspension fix was the reverse of the front fork. We dropped the stock 5.6 rear shock spring for a softer 5.4, set the low-speed compression adjuster at three clicks out and the high-speed adjuster two full turns out. This set-up, when paired with the stiffer fork springs, brings the superb CR500 chassis into balance.
We preferred to set the race sag at 95mm (even though Honda recommended 105mm). The stouter sag keep the rear end up, helps the bike turn and cuts down on packing under acceleration.
1999 YZ125: ANYTHING ELSE?
I have a 1999 YZ125 and I would like to know the best fork settings I should have for my bike. Anything will help thanks a lot
You are asking us to go back seven years, but we think that we can help you. Here are the things that we worked on with the 1999 YZ125.
In '99 Yamaha changed the length of the Kayaba shock, the nitrogen volume, shock valving, linkage pivot location and shock shaft speed, but in reality they changed very little. How can that be? The shock is 15mm longer, but the shock linkage is 12mm lower. So, the difference is minimal. The rising rate was changed so that shock shaft speed in the initial part of the travel was increased to provide a suppler ride, but the valving has been increased for more compression. When all is said done, the rear suspension didn't change much for 98 to 99.
Our best setting back in 1999 was:
Spring rate... 4.6 kg/mm
Compression... 15 clicks out
Rebound... 16 clicks out
Shock Note: The 99 swingarm, linkage and rear wheel were two pounds lighter than the 1998 model. A large percentage of this is unsprung weight (the hub), which results in more active suspension response. The rear follows the ground better than last year and has less of a tendency to thud through the whoops.
Avoid setting the race sag at 100mm. The Yamaha chassis works best with the sag set higher than on a Honda, Suzuki or Kawasaki. Faster riders will run less and less sag.
The 1999 forks were set up for a 150-pound rider the stock forks are fairly sweet. Bigger and faster riders might want to up the stock spring rate from 0.41 to 0.42. One of the problems with the 1998 Kayaba forks was their tendency to drop into the travel and hang there. Stiffer springs helped keep the '98 forks up, but for small riders the stout springs increased midstroke harshness. For 99 Yamaha stiffened the blow-off valve on top of the cartridge rod and reworked the infamous mid-valve. The result? The YZ forks stay higher in their stroke (keeping more travel in reserve for middle-size bumps).
Our best setting for the 1999 forks were:
Spring rate... 0.42 kg/mm (0.41 stock)
Compression...7 clicks out
Rebound... 5 clicks out
Fork leg height... 5mm above top of stanchion
Fork Note: The '99 YZ125 was sensitive to fork height. In order to get the YZ125 to turn sharply we had to raise the fork legs up in the triple clamps. Place a zip-tie around the fork leg to determine whether or not the forks are bottoming. Use this as a guide to compression clickers and oil height.
2001 HONDA CR250: THE BIG PICTURE
I have a 2001 Honda CR250 and have difficulties dialing in the shock. I was wondering what were the suspension settings the MXA test crew found best for this bike back in 2001.
We will try to help you, but it should be noted that MXA felt that the 2001 Honda CR250 had several suspension flaws. This gets a little longso sit back and relax.
The 2001 CR250 begs for a stiffer shock spring. The stock 4.8 kg/mm spring rate will work for riders who weigh less that 160 pounds, but everyone else will be happier with a 5.1 (and the faster or heavier the rider the higher the spring rate).
How can you tell if you need a stiffer shock spring? (1) Set the ride height on level ground at 97mm. (2) Check the shock's free sag. Does it have any? (3) If the free sag is less that 15mm, you need a stiffer spring.
If you don't get the correct spring on the 2001 CR250 shock expect it to drop into its stroke in G-outs, landings and whoops. You can also expect it to unweight and kick in braking bumps? Why? Because a soft spring has to have a ton of preload cranked into it to get the proper ride height. This extra preload does not make the end-rate of the spring any stiffer, but it does produce a tendency for the unloaded spring to kick back with a vengeance. Put on a 5.1 and you'll be happier.
Once you have established the spring rate that works best for your weight or skill, use the high-speed compression adjuster (the big dial) to determine the chassis' attitude under acceleration. We ran the high-speed compression at one turn out (it is in the standard position when the punch marks are aligned). Use the low-speed compression clicker to tame down the kick. The Honda is prone to kicking over braking bumps and finding the lightest compression setting for the conditions is essential.
What was our best setting?
Spring rate... 5.1 (4.8 stock)
Hi compression... 1.25 turn out
Lo compression...9 clicks out
Rebound... 9 clicks out
Shock Note: The Honda chassis is attitude sensitive. If the rear hangs down the forks will feel stiff and rigid. If the rear sits too high, the front end will feel like it has dropped into its travel. You have to fix the rear end before you can finalize a front fork setting.
For 2001 Honda worked very hard to get the harshness out of the CR250 forks. The went to the next stiffest spring (0.44 kg/mm) and lightened the compression damping. Good move. For light riders this set-up is about as good as showroom stock Honda forks got up to this point. But, the forks exhibited midstroke harshness, a dead feeling and a tendency to hang down in their stroke.
MXA's solution to the perceived 2001 CR250 problems were:
(1) To keep the front end high in its stroke over mid-sized bumps we put an optional stiff Honda fork spring in one leg. With a 0.44 in one leg and 0.45 in the other we increased the overall spring rate just enough to keep the front end higher in its stroke without adding too much stiffness;
(2) We didn't think the stiffer fork spring will work without the stiffer shock spring. The two work in conjunction. The rear spring holds the rear higher, which loads the front fork more, and allows the stiffer spring to have about the same compression rate as the stock fork springs, but without the stinkbug feel;
(3) The final step is to lower the oil height in small increments until you get the supplest feel out of the forks without bottoming. For us, that magic number was about 7cc per fork leg.
(4) Use the clickers to fine tune the feel of the fork in the second half of the stroke. Try to run the clickers as far out as possible, but be careful not to go too light on the rebound.
What was our best setting? For hard-core racing we recommend this set-up:
Spring rate... 0.44/0.45 (stock 0.44)
Oil height...376cc (stock 383cc)
Compression...14 clicks out
Rebound... 14 clicks out
Fork leg height... 7mm up (with 21" tire)
Fork Note: It's important to remember that the compression adjuster is on the top and rebound is on the bottom.
FUEL INJECTION: THE WHOLE TRUTH
Everyone says that the 2007 bikes are going to be fuel injected, but MXA says that it won't happen until they get better sensors and more testing time. What's the real story?
The odds of there being fuel-injected motocross bikes for the 2007 season is slim (and none would be a good bet). Why? Here are three good reasons:
(1) The business of manufacturing motorcycles centers around making money. To make money, a manufacturer needs to control costs, which means that they need a stable product line that they can sell for several years without incurring excessive R&D costs. Fuel-injected motorcycle would require new gas tanks, new airboxes and new throttle bodies, plus fuel pumps, swirl tanks and, most importantly, new cylinder heads. Investing in that technology for production wipes out the profit, even if it sells more motorcycle. It takes a few years of product stability to pay off development cost. Most of the Big Four, have just recently introduced new machinery that could use 2007 as a year of modest change to help the bottom line.
(2) MXA does carp about sensors because fuel injection depends on the information fed to the ECU to determine how much fuel to spritz. At the very least a fuel-injected motocross bike will need a manifold pressure sensor (downstream of the throttle body) or an oxygen sensor (upstream of the throttle body). Either will work, but both will have to calibrate barometric pressure to determine oxygen content of the surrounding air. Next, fuel-injected bikes will need a throttle position sensor. Keihin carbs have roller sensors on their slides, but a fuel injector's throttle body will have a butterfly. To do the logarithms, the ECU will have to compare throttle position and oxygen density to choose the correct fuel map. Finally, fuel injection will require a temperature probe of some kind...if, not as part of the map's calculations, as a fail safe for engine failure.
(3) There is something called the "penalty of taking the lead," and the first fuel-injected motocross bike will have to pave the way for all of those that come after. That means that it will have to make the mistakes, swing public opinion and suffer the slings and arrows of any flaws in the technology. It's not that no one wants to be first--it's that no manufacturer wants to be first until they are absolutely positive that they have fuel injection perfected.
All that said, there will be fuel-injected motocross bikes in the future, but maybe not in the immediate future.
CR65 & YZ65: WHERE ARE THEY?
Why don't Yamaha and Honda produce 65cc class motocross models for younger riders?
Yamaha and Honda don't make 65s anymore because it was not profitable for them (both did have Junior Cycles at one time). The total 65cc market, split between Kawasaki, KTM and the Suzuki version of the KX65, is around 6000 machines. Honda and Yamaha figure that if they entered this market their share would be a subdivision of the total market. The numbers, when divided by five, would become too small to justify the R&D costsso they are willing to let KTM and Kawasaki have the market.
TWO-STROKES: LIFE AND DEATH
Will Kawasaki produce two-strokes in '07? Shouldn't there be two-stroke-only classes in amateur racing to keep the 125 and 250 two-strokes alive?
Kawasaki stopped importing the KX125 to the USA in 2006 (although they still made the bike for other countries). Although Kawasaki will still sell the KX250 in 2007, it won't stay in the line-up in future years if sales decrease as much as most analysts predict.
The Schoolboy class has been set aside as a 125cc two-stroke-only class, but this is a stop gap measure (much like the shaft-drive Pee-Wee class was started to save the Yamaha PW50). With decreasing two-stroke sales, the idea of having classes for them becomes mootsince very few of them will show up at the race tracks in the next two years. It would be nice to try to save the low-cost and effective two-stroke, but the AMA's double-the-displacement rule for four-strokes has made that an impossibility. The only thing that will save the two-stroke is if thousands of American racers rushed out and bought a 2007 model. The power is in the hands of the consumer--but only for a short time.
THE FABLED AND SHORT-LIVED CLAIMING RULE
I have heard stories of a privateer who actually was able to take advantage of the claiming rule and scored himself a one-off factory works bike. I, along with many others, would love to know all of the details!
There was a claiming ruleright up until someone actually claimed a bike and won itthen th AMA dropped the rule. The idea behind the rule was to lower the cost of racing, and keep the privateers from being slaughtered by works bikes, by setting an established price for every bike in every AMA national. For $3500 any rider who was in the same race could claim the Winning rider's bike. In essence, it was suppose to keep the costs down (and remember that $3500 was a lot of money back in 1977).
Mickey Boone was the first rider to try and claim a works bike (Marty Smith's CR125), but Honda put in a counter-claim for Smith's bike and Boone lost it. Although there were several other claiming incidents, it wasn't until John Roeder claimed Marty Tripes' 250 Honda that a privateer actually won a bike by claiming it. At this point the AMA had watered down the rule so much that they allowed multiple claims on the bike (and all the team managers carrying checks for every one of their riders to make counter claimsand, if an opposing team won the claim, they would give the bike back to the other factory). John Roeder claimed Tripes' bike and 14 factory checks were thrown into the claiming pool. Roeder won.
One week later the claiming rule was dropped from the AMA rule book.
2006 YZ250F: HANDLEBARS HEIGHT
My son and nephew recently got the new motocross bikes and the bug bit me hard! After 25 years away from dirt bikes, I purchased a 2006 Yamaha YZ250F. In your test of this bike it was recommended to raise the handlebars by 10mm. Can you please recommend where I might purchase new mounts for my stock clamps?
The easiest way to get the taller handlebars is with taller handlebars. Every bar manufacturer makes a "YZ-high" bar and, amazingly, taller bars cost about the same as taller bar mounts. We used ProTaper "YZ-High" bars. The stock YZ-F bars are 80mm high with a 50mm sweepyou can compare handlebars charts from Tag, Renthal, Azonic and ProTaper to find any bar that is 8 to 10mm higher. The 2007 Yamaha's will have taller bars.
SUZUKI RM-Z450: WHITE PLASTIC
I want to white my RM-Z450 out like Nick Wey's CRF450. I have an all white plastic kit but there are no all white graphics for my bike. Do you have any suggestions?
We've had the same problem, but the solution is simple. We find the style of graphics that we like and we cut, with scissors or X-acto knife, the color elements that we want.
Graphics are kind of weird in that the use the same color of 3 mil vinyl to cover plastic of the same color. One Industries RM-Z450 TechnoFlex Graphics have a reasonable amount of white and only a little bit of yellow. Go to www.oneindustries.com to look that them.
WORKS BIKE VERSUS PRACTICE BIKE
What is the difference between a factory rider's practice bike and their race bike?
Every race team is different, but normally a factory rider has three different types of bike:
(1) Race bike: This bike is used only at races. It is pampered and cared for during its whole life cyclewhich is approximately four to five races for a factory rider.
(2) Test bike: Each team will have various bikes that are used for testing. They are identical to the race bike except for the fact that they are used during the weekdays to test various performance products and ideas at the test tracks. The test bikes swing back and forth between being in perfect condition and being well used. Test bikes do get overhauled constantlyso while they are well usedthey are mechanical perfect. They could be raced in a pinch and are sometimes used for races like the Prequel. When the test bikes starts to show its age it can get demoted to a dyno bikewhere it is used in the shop to test head mods, pistons and pipes.
(3) Practice bikes: A practice bike has the suspension and engine mods of the race bikebut leads a hard life (normally cared for by the rider and his helpers) it doesn't get the loving care of the race bike. The rider's mechanic will keep it running, but with most factory riders living for states without income tax (Florida and Texas), the in-house factory mechanics normally only work on the bike occasionallyleaving the rider on his own for longer periods of time. Practice bikes get thrashed very quickly.
2005 YZ250: FRATERNAL TWINS
In the article on race mods for the 2006 YZ250, did you perform the exact same mods on the 2005 model, which is what I have?
Yes, with the exception of the SSS suspension, the 2006 YZ250 is virtually identical to the 2005 in terms of mods.
YAMAHA YZ250F: GOING FLAT ON TOP
I race at tracks around Phoenix, so it is close to MXA's SoCal tracks. My YZ250F feels like it goes flat at high rpm. It is all stock except for accelerator pump. Can you help me fix it?
As you have already discovered four-stroke jetting issues, while minor in comparison to some two-strokes are much harder to diagnose (and when it comes to changing a jet they are a nightmare to work on).
First off, Jetting-wise we don't think you will find any major differences by making changes. We can suggest four approaches, but they are theoretical in some aspects.
(1) Occasionally we change the pilot jet...going slightly larger in warm air and a lot larger in the winter (cold air).
(2) You can try a bigger main, but we called Doug Dubach, Yamaha's test rider, with your question and he said that in rare instances a main jet might help, but that the YZ250F tends to rev fairly high while feeling flat in the upper end. He said that it is part of the engine's nature. He wondered if you were coming from another brand, which might have been crisper on top which makes you more sensitive to the feel of the YZ250F.
(3) The quickest fix is an aftermarket pipewhich picks up the rev on top and fills in the gaps.
(4) Although the pilot jet change doesn't really affect the top-end, sometimes a richer pilot and the perfect fuel screw setting, make the engine quicker across the middle and able to carry farther in the top. So you fix a problem at one end, by maximizing the other.
HONDA CRF250: BURNING OIL
Recently after racing a 3-hour hare scramble, I noticed that my oil height in my CRF250 dropped more than usual after a race. It was maybe 1/8" lower than normal on the dipstick. This track was a very sandy, fast and high rpm track. Would this be a reason for the reduced oil height or is there another reason?
Many four-stroke riders don't realize that their bikes burn oil in much the same way as a two-stroke. You lose a little when starting the bike, some blows by the rings and some is lost to normal wear and tear.
It doesn't seem unusual to use a considerable amount of oil on a CRF250 in a three-hour race. The addition of sand and high rpm running is obviously a contributing factor. Just the fact that the race was three hours long meant that your rings were three hours older at the end of the event than they were at the beginning.
If you don't see smoke, the overflow tube isn't blowing oil into the airbox and the crank seals aren't leakingwe would assume that your oil loss is natural for the event you raced.
The key element is that you check the oil and keep track of itmany CRF250s have fallen victim to rider's who don't want to take the time to look at the dip stick. Unfortunately, a sight glass would be a worthwhile addition to a CRF250, but Honda claimed that there wasn't enough room on the CRF250 cases.
2006 YZ450F: POPS AND BOGS
My 2006 YZ450F pops at low rpm, when decelerating with the throttle off and it doesn't want to idle. Also, it won't start without choke even when warm. Have you guys experienced something similar with this model?
Your problem is not uncommon and the fix is relatively simple. The standard pilot is 42. We have had luck fixing this problem with a 45, 48 or 50 pilot jet. The choice depends on how severe the problem is (you be the judge). We would start with a 48, since summer is coming, but order a 50 pilot for winter.
YZ125: PAGING FOR RICK PETERSON
I Hope you can help. I read an article in an old MXA about an RPMS big-bore kits for the YZ125. Could you please let me know the e-mail address for them. I contacted them last year, but I have since changed computers without keeping my favourite links. I want the 134cc kit.
You can find out about Rick Peterson's big-bore engine kits at www.maxrpms.com or (608) 224-2524
SPEED VERSUS OLN: BETTER OR WORSE
Do you know if Speed is showing the AMA outdoor Nationals? I know they showed every Supercross. I hope they cover the Nationals as well.
The AMA Nationals will be shown on OLN (the Tour de France channel) on a week delay--and a longer delay during the Tour.
BRAKE FLUID: KILLING ME WITH KINDNESS
When dealing with brake fluid, I have always been told that the higher the "DOT" number, the higher the quality, boiling point, resistance to moisture, etc. Based on this theory, DOT 5 (or in this case, Motorex DOT 5.1) should be superior to the DOT 4 that is recommended for my CRF450R. However, it seems like I read in your magazine somewhere that you should never use DOT 5 Brake Fluid - can you clarify this for me?
We're not sure how detailed you want to get. Suffice it to say that we recommend either DOT 4 or DOT 5.1. If you accept that answer, don't read any furtherbecause from here on it gets boring. You can expect your motorcycle to be floored with low-cost DOT 3 fluid. It is best to replace it after break-in with a racing DOT 3, 4 or 5.1 fluid (preferably with one that carries the highest dry boiling point you can find).
In almost all cases DOT 3 is the least expensive and lowest performing brake fluid produced. The exception to this rule is Maxima DOT 3 550 with a 568 dry boiling point (the highest of any stateside-produced motorcycle brake fluid).
Base: Synthetic Polyglycol base.
Dry boiling point: Minimum required dry boiling point-401 degrees.
Wet boiling point: Minimum required wet boiling point-284 degrees.
Viscosity: Viscosity at minus 40 degrees-1500 cst.
Compatibility: DOT 4 & 5.1.
Most DOT 3 fluids meet DOT 4 regulations and vice versa (save Motul's Racing Brake Fluid 600, which has incredibly high dry and wet boiling points of 585 and 421 degrees). Motul 600 exceeds DOT 3's 1500 cst viscosity rating by two percent (at minus 40 degrees) to be labeled as such.
Base: Synthetic Polyglycol base.
Dry boiling point: Minimum required dry boiling point-446 degrees.
Wet boiling point: Minimum required wet boiling point-311 degrees.
Viscosity: Viscosity at minus forty degrees-1800 cst.
Compatibility: DOT 3 & 5.1.
The high boiling points of DOT 5 made DOT 5 the hottest fluid going in the late 80s (now only Harley-Davidson spec's it). But the fluid's syrupy nature wreaked havoc on the system if water or air entered. Since thick brake fluid won't allow microbubbles to float to the top of the reservoir, unwanted air is dispersed throughout the system (making lever action mushy). Unlike a Polyglycol fluid, silicone-based brake fluids do not absorb water. Instead, the heavier water settles toward the bottom of the hydraulics, where the caliper resides. That means a liquid with a low boiling point is residing in the area that generates the most heat. If not bled, the caliper can also corrode.
Base: Silicone base. DOT 5 is purple. The purple color is a DOT mandate indicating a silicone base that cannot be mixed with the yellowish DOT 3, DOT 4 or DOT 5.1 fluids. When mixed, the fluids coagulate and turn to Jell-O. Unlike DOT 3, DOT 4 and DOT 5.1, DOT 5 will not damage painted surfaces.
Dry boiling point: Minimum required dry boiling point-500 degrees.
Wet boiling point: Minimum required wet boiling point-500 degrees.
Viscosity: Viscosity at minus forty degrees-900 cst.
Compatibility: DOT 5 silicone base
DOT 5.1 is a European-produced fluid came into existence due to the fast moving, anti-lock braking systems (ABS) used on today's automobiles. DOT 5.1 is the thinnest fluid and offers the least hot-to-cold change in viscosity. This fluid has the highest wet boiling point of any of the synthetic Polyglycol.
Base: Synthetic Polyglycol base.
Dry boiling point: Minimum required dry boiling point-500 degrees.
Wet boiling point: Minimum required wet boiling point-356 degrees.
Viscosity: Viscosity at minus forty degrees-900 cst.
Compatibility: DOT 3 & DOT 4.
2006 KTM 525SXF: FUTURE TEST RIDER
I'm coming from 2006 CRF450 with a resprung/revalved MB1 set up, Ti shock spring, oil lock collars, works bladder and cap, etc. to an MX Tech revalved/resprung 2006 KTM 525SX. Mike Battista's work was excellent. Plush, able to ride effortlessly through chop, and coming up short was no problem. With my WP stuff, I can't say the same. I've tried the sag from 105 to 115. Played with HSC, LSC, compression, rebound, etc. I got the bike to where I can ride it reasonably fast, but I don't have 100% confidence in it. On more technical stuff the chassis seems to flex and be a little more active than my CRF. The front end seems to understeer a bit on corner exits. Overall the bike just seems less forgiving than my Honda and reacts more to sudden hits or rider mistakes. My question is, are these more of a KTM tendency or can you offer me some baselines to get it a little more forgiving on the big hits?
You have the makings of a test rider. In truth your evaluation of the differences between a Honda CRF and KTM is very accurate. The problem is that your assessment is so spot-on that you have discovered the inherent shortcomings of KTM's overall designshortcomings that are hard to iron out.
When KTM's suspension is set-up for hard, fast hits (so that it won't bottom or bang) it is wallowy over the small stuff. When you get it dialed in for chatter bumps and the rolling stuff, it rockets through the stroke on the big stuff. Such is the life with KTM's current rising rate. Worst of all, KTM's don't like low-speed, high-load G-outs. By that we are talking about slow shock shaft speeds, with considerable downward weight on the suspension (like dropping into a corner from a hump in first or second gear). Nothing can stock the WP shock from bottoming out at slow shock shaft speedsit is a rising rate deficiency. There is no comfort in knowing that the 2006 bikes are much better than older KTM's in these areas.
The KTM chassis does flexthis is most noticeable on the entrance to turns when either the chassis pendulums back and forth when the front tire is planted or the front end see-saws when the rear wheel is planted. We call this clanking (and the CRF450 is not immune to clanking at the entrance of turns, but there's was a geometry problem). KTMs clank is caused by a combination of frame flex and slack geometry. Next year's KTM will have a much stiffer steel frame.
All KTM's understeer from the center outwe like to call this "Euro Handling." The 525 doesn't push worse, but because of its big-bore engine and added torque it should because the engine tends to chug the chassis into the turn instead of around it.
We can't really help you with baseline settings for an MX Tech shock because it will be much different than the stock stuff. We know that we haven't offered you any help, but we are impressed with your evaluation of your problem.
MOTOR MOUTH VERSUS ENGINE MOUTH
As I spend the next year in Iraq, Motocross Action Magazine is my fix to ease my motocross addiction. Aside from my family, the riding and tinkering on the bikes is what I miss the most over here. With 3 boys and a wife that rides, there is always work to be done on the bikes, so the "Ask the MXperts" is the section I read after I finish "Jody's Box." I had to smile when I saw the "Engine vs Motor" question in the May 2006 "Ask the MXperts." It was a flash back to my powerplants instructor in college. He held a Ph.D. in electrical engineering, and made a habit of driving home the difference between the two. That lesson served me well for many years flying for the Navy and then the airlines. Now, while relaxing and reading about my favorite hobby, I'm reminded once more. It is a small point, but it just showcases the knowledge that MXA is able to share in an entertaining way. Thanks for helping pass the time over here, keep up the great work.
Thanks for your letter. We, like you, have always been sticklers about the difference between an engine and motoryet the word still manages to make it into the magazine on occasion (and every other magazine constantly). Your letter was one a several on the subject, but most started with the phrase "Well, why is called a motorcycle and not an enginecycle?"
HONDA XR200: JUST THE FACTS
I have a Honda XR200 dual bike, which has a 4-stroke engine with a displacement of 200cc. It's listed as having an output of 19 horsepower. I have the following questions:
1. Why is there a huge gap between the hp produced by this bike and bikes like the CRF250 and CR250?
2. What is the difference between motocross biking and off-road biking?
3. What are the differences between motocross bikes and off-road bikes in terms of design and performance?
The huge gap in horsepower is the product of the extra 50cc, higher compression and Honda's intent. Honda did not intend for the XR200 to be raced. They focused on reliability and cost issues instead of horsepower and a $6000 price tag. The XR200 is a trail bike. It was built to last for years and one of the easiest ways to increase longevity is to decrease horsepower. Motocross bikes are full-race machinesalthough they will last an acceptable amount of timethey wear out much faster than a trail bike.
The difference between off-road riding and motocross is that MX is an all-out race. The riders go as hard as humanly possible and stress their machines to the fullest. The course is especially built to be very challenging. Off-road riding takes place over natural terrain, for longer distances and with lower intensity. An off-road rider does not face man-made obstaclesnor can he go ten-tenths over terrain that he is unfamiliar with.
A motocross bike has very stiff suspension, powerful (and sometimes harder to use) engine output and an emphasis on light weight. Off-road bikes have much softer suspension, easier to use (and broader) powerbands. Off-road bikes tend to be heavier and are often equipped with rudimentary lights, lighting coils, kickstands and larger gas tanks.
2005 CRF250: CLOSING THE BIG GAP
I have a 2005 CRF 250R and want to know what the best gearing is for MX tracks? Right now I'm using a 13/50. I heard Hondas have a big gap between second and third and the only way to fix it, if your not on a factory team, is to change the gearing.
As a rule of thumb we automatically suggest adding a tooth to the rear sprocket of the 2005 CRF250. On hard dirt the stock gearing is passable, but once you hit deep loam the engine will be reluctant to make the second-to-third upshift without falling off the pipe. Going to a 52-tooth rear sprocket will bring third gear closer to the meat of the motor.
There is paradoxically a different school of thought that says you should opt for a 50 (one tooth less). We actually ran a 50 in 2004 because it allowed us to use second longer so that we didn't have to shift to third on the exitwhere it tended to go flat. With some modest power increases in 2005 and 2006, we have given up on the 50 in favor of the 52, which punches up the bottom end, brings third gear closer to second and improves throttle response.
IN SEARCH OF ICAT
I have been reading about the iCat. What is the deal with it and does it actually work by creating a more efficient burn?
We have tested the iCat, but our experience is limited to the bikes we tried it on. An iCat doesn't increase the voltage, instead it spreads the duration of the spark out. All modern CDI-equipped ignitions produce more than enough voltage to ignite the fuel/air mixture, but according to the iCat designers--the spark doesn't last long enough. The stock discharge voltage is high, but only last about 10 nanoseconds. The short duration of the electrical discharge means that some fuel is left unburned or, at the very least, the combustion is not simultaneous enough to maximize power. Energy is lost when partially unburned fuel is passed into the exhaust system as noxious gases. The iCat electrically alters the shape, speed and profile of the spark to make it last longer.
The iCat is not a capacitor-style spark boosters, like the old Roost Boost. We never like Roost Boost because of the lag between ignition timing and capacitor buildup.
We tested the iCat on two bikes (back in 2004) a YZ250 and CR125. On the YZ250 it gave the impression of crisper jetting and better throttle response (but not impressively so), while on the Honda CR125 it invigorated the complete powerband (impressively so). We would surmise that good powerbands don't benefit as much as bad ones (thus the ecstatic response on the CR125). The iCat reps also told us that the iCat didn't do anything for the 2004 RM125.
We haven't tested it since 2004and since you didn't say what kind of bike you were putting it on (in addition to our mixed results with the bikes we tried), we can't give you a definitive answer.
2005 YZ250F: SPROCKET SIZE
What size sprocket did you find the best for a 2005 YZ250F? I read that you like a tooth higher on the 2002, what about the 2005?
We left the 2004 and 2005 gearing stock. The YZ250F has gained some power since 2002 and with more power we didn't feel the need to gear it down for most tracks. Of course, tighter tracks wouldn't be hurt by one tooth on the rear to help it get out of corners with a little more authority.
What cave has MXA been living in? In the Fuel Injection article in the June 2006 issue you said, "but that is only because it doesn't (fuel injection) come stock on any bike." What you meant to say is that is does not come on any of the big four yet and that Cannondale was the FIRST! And that was done 4 or 5 years ago, way ahead of any of the others. But it is painfully obvious that the Cannondale will never rate any print or have done anything first in your eyes since a big check is not associated with it. If this bike has any claim to fame, it's the FIRST AND ONLY fuel injected motocross bike made and totally legal to race in the AMA. A correction is in order.
Dream on! Fuel injection came stock on the ATK 604 years before Cannondale even existed (which negates your FIRST AND ONLY claim). It should also be noted that ATK sold 1500 bikes a year for decadesunlike Cannondale that barely sold any bikes. We'll stick with the phrase, "but that is only because it doesn't (fuel injection) come stock on any bike" because we are talking about bikes that people can actually buy in showroom today (not brands that went out of business years ago).
We appreciate your loyalty to your favorite brand. Scott and Joe Montgomery would be proud--if only they had anything to do with Cannondale anymore. Your "big check" comment is idiotic and insulting. We have chosen the Suzuki RM250 as the best 250 two-stroke for three years running and Suzuki was not an MXA advertiser for the majority of that time. We are often criticized for choosing Yamahas based on the assumption that Yamaha is our biggest advertiser. Not true! Honda is our biggest advertiser. Contrary to your logic, if we were as crass as you insinuate it would have behooved us to write nice things about Cannondale so that they would have sold a lot of bikes and become a big advertisers--but the truth is that the bike was flawed and our responsibility is to the consumer. The fact that you have dedicated your life to Cannondale is admirable, but it doesn't make a silk purse out of a sow's ear.
No corrections are in order.
GASOLINE: HEADING FOR THE HILLS
I plan on spending the summer riding in the Mammoth Mountain area, but I am confused about what fuel to run. My buddy says that because of the lack of oxygen at high altitude that I will need to run 100-octane race gas in my bike. Is this true?
No. Cylinder pressures are lower at high altitude, so you don't need extra octane. Just buy pump gas at the local station and don't worry about high octane.
2004 RM125: OFF THE CHART SAG
I recently purchased a 2004 RM125 and I was wondering what settings you guys found best for the bike. I weigh in at around 150l pounds. At the moment the front end seems to be all over the place. My current sag is set to 100mm. but the static sag is at 55mm!!
Your static sag is off the chart. The 2004 Suzuki's suspension was way too soft. Slow, light and ex-mini riders can get away with the stock suspension, but heavier or faster riders must stiffen up the suspension right away. In our opinion, the best thing you can do to the 2004 RM125 is throw a stiffer set of springs at it front and rear. The forks need 0.43 kg/mm fork springs to help them stay up in the stroke. With the next stiffest fork springs we were able to run the compression and clickers at 10 out, which leaves lots of room for adjustment.
As soft as the forks were the rear shock was even more buttery. Suzuki completely redesigned their linkage for 2004, but with the stock spring rate the rear end felt like a giant pogo stick. With the stock spring rate we had to run the compression at 3 and the rebound at 4 just to get the rear end to settle. We switched the stock 5.0 kg/mm spring for 5.2 and couldn't believe the difference. Let body weight be your guide. Under 140, try to run it stock. Over 140, go stiffer.
We ran the rear suspension with 98mm of sag, the compression at 10 out and the rebound on 12.
On another note, we dropped the mainjet to a 380 and ran a half clip leaner needle, but this will depend on your local conditions.
2005 YAMAHA YZ250: SUSPENSION
I just bought a new 2005 YZ250 two-stroke. What are MXA's suspension settings & sag amounts?
With every model year Yamaha has tried to lessened the YZ fork's tendency to bottomand 2005 was the first year that they succeeded. The 2005 AOSS (air oil suspension system) forks were way better than anything they previously offered. Although the 2006 SSS (speed sensitive suspension) forks are much better than AOSS.
The 2005 AOSS forks resisted bottoming, absorbed little bumps with ease and didn't get harsh over the medium-sized stuff. But, they really tend to slow down quickly at the end of the strokewhich is jolting in high-speed bumps The average rider should start with the compression on 12 out and the rebound on 10 out (and turn in compression in to eliminate divinguse the dust line on the fork leg as your guide for compression).
For 2005 Yamaha upped the shock spring rate from 4.75kg/mm to 4.9 (which is what we ran in 04). You would think that the spring rate change would make the new forks feel like our modified forks from the year before. Nope. For 05 we raised the shock spring from a 4.9 to a 5.0 or 5.1 (depending on rider weight). If you weigh over 175 pounds or go faster than the typical rider, go stiffer. We made the swap and loved the plush feel. Depending on your track, set the rebound on 12 clicks out and the low-speed compression on 12.
CRF450 STEARING: AGAIN
I have been reading the info you have given on steering geometry for the CRF450's. I feel my 2006 understeers, so would putting a set of 20mm RG3 clamps be a waste of time with the geometry it already has?
More than likely putting 20mm offset triple clamps on your 2006 CRF450 would aggravate the understeer. Less offset (going from 24mm stock to 20mm) increases trail (which is a measurement from where the virtual head tube hits the ground backward to the center of the front wheel's contact patch), increased trail improves stability, but is really not conducive to rapid cornering. The best way to move towards oversteer is to lessen trail or increase the head angle.
The paradox in this scenario is that from 2002 to 2004, the understeering CRF450 was fixed by increased trail, but that had to do more with other inherent problems in the early CRF chassis. In 2005 (and thus 2006) Honda made a boatload of frame changes and they changed the fork offset (at the front axle instead of at the triple clamp) at the same time.
You will have better luck in lessening understeer by sliding your forks up in the clamps, which will steepen the head anglea bigger contributor to turning prowess than any other number on a bike's chassis.
SAVE OUR TRACK
There is a place in Georgia called Durhamtown, which for some reason is under attack by the state and the local new media. There have been some injuries and a few deaths, which are unfortunate, but a grim reminder of the danger of this sport. Durhamtown is a safe place to ride. The owner has many rules that every rider must follow (i.e. helmets, one-way trail, speed limits in heavy travel areas). There are EMTs on site every weekend. Durhamtown personnel patrols on all the trails and trail sjust for beginners. What can we (hundreds of rider who enjoy this place every weekend) do to help this place we love.
Over the years, we have seen this scenario take place at local tracks many timesand in most cases it is difficult to organize a loose and casual group of riders to do anything until it is too late. But, I do know thisthe bad publicity that hurts a track can be turned into good publicity through the same media. As much as Cycle News, MXA and Racer X may seem like media sources that can helpwe are preaching to the choir. You need to go to the same local media sources that are part of the problemnewspaper, TV and radioand help educate them to your side.
How do you go about this? Good question. Here is what other tracks have done: Offer the track for local charity events; hold ride days; invite the morning news crew out to do a feature (teach the reporters how to ride and bikes like a CRF150 or TT-R125); Make phone callsnot to whine about bad coverage, but to suggest good coverage.
Lots of facilities, from airports to race tracks to BMX parks to hunting clubs, are under attack. The ones that survive are the ones that can make a meaningful connection to the community. A track keeps kids off the street. It is a family sport. A track can be a great way to keep people from riding illegally (this was the pitch that drag racing tracks used in the 60s).The track should adopt a local charity and make connections with the public servants.
This isn't easy to do, but you don't win a war by fighting hand-to-hand with a TV exec or a newspaper editor or the mayoryou win it by winning over convertsfrom cub reporters to the children of the mayor.
We hope you can rally the troopsbecause that is really the hardest job.
2006 YZ250: SET-UP
Based on your test the 2006 YZ250 it sounds like it has a ton of potential to work great, but I seem to be struggling with mine a bit. This is my third YZ250, so I'm not exactly a rookie at this game. Any settings you found to work well would be greatly appreciated for me to use as a baseline.
Since you have experience with the YZ250 you probably understand the importane of the new 2006 suspension components. Last year Yamaha used AOSS forks. AOSS stood for Air/Oil Separate System. The 2006 forks are called SSS for Speed-Sensitive System.
There is two types of damping: position-sensitive and speed-sensitive. Last year's AOSS forks were 70 percent position-sensitive. The damping rates were dictated by the position of the fork's piston inside the cartridge rod. In simple terms, The farther the piston moved down in the cartridge rod, the stiffer the damping. On your 2006 SSS forks, damping is 90 percent speed-sensitive. By switching from 30 percent speed-sensitive damping to 90 percent for 2006, the forks will stay higher in their stroke, have a more linear damping rate and resist bottoming. Speed-sensitive damping gets its name because the damping rate is determined by the speed at which the piston moves though the cartridge rod. Yamaha's speed-sensitive damping has a more linear damping curve. A linear curve gets steadily firmer as it goes. There are no hills or valleys in the damping curve. It gets stiffer at the exact same rate in the first half of the travel as in the second half.
In our opinion, the SSS forks are better on every size bump than the previous YZ250 units, which fought back at the end of the stroke. SSS damping is regulated in such a way that the spring rate had been reduced from 0.44 kg/mm to 0.43 kg. They resist bottoming, absorb little bumps and don't get harsh over the medium-sized stuff. The average rider should start with the compression on 12 out and the the rebound on 10 out.
As for the rear shock, it is very modern: The 2006 shock has an 18mm shock shaft. That is 2mm larger than last year's shock shaft. The larger shock shaft displaces more oil, which means that more oil is pushed through the valving sooner, which results in a more sensitive feel on small chop. All the internals parts of the YZ250's Kayaba shock are Kashima-coated to reduce friction. In addition, the shock reservoir has been increased in volume by 30 percent larger reservoir to help control the heat. The shock spring is made from titanium. It is rated as a 4.9 kg/mm spring. Last year we suggested a stiffer spring for riders over 180 pounds, but in testing stiffer springs this year we didn't like the feel.
Once you have it dialed in it is a very good shock. We ran the race sag at 100mm, high-speed compression on one turn out, low-speed compression on 11 clicks out and rebound on 9 clicks out.
Remember, those are just starting points that you can work off of for your local track conditions, weight and speed.
KTM 250SX: ALL YOU NEED TO KNOW
I just got an 2006 250SX and am looking for a base setting for suspension and jetting. I'm 6' 3" and 195 pounds before gear (with long legs). Will the stock springs work? I ride outdoor MX and an occasional cross0country. Also I believe you recommend a certain PC pipe?
Here are a few tips for your KTM 250SX:
(1) Springs: You will not need stiffer springs. It should handle a 195 pound rider of your height no problem.. In fact, the KTM is one of the better bikes for tall riders in terms of ergos.
(2) Pipe: Pro Circuit built a special pipe for Jeremy McGrath, when he was riding a KTM, and while Jeremy never really got full use out of it, Pro Circuit does sell Jeremy's pipe. It is very very good.
(3) Jetting: In the warmth of summer the stock jetting will be okay, but you might want to lean out the 42 pilot to a 40 and go for the optional NIEG needle over the stock NIEF (the NIEG is a half-clip leaner and comes with the bike).
(4) Forks: We ran the fork caps 5mm up in the triple clamps (remember, the 2006 forks raise the front of the frame higher and thus can be slid up into the clamps much more than previous KTM forks). Our best settings were with the compression on 16 clicks out and the rebound at 18 clicks.
(5) Shock: Set the high-speed compression at 2-1/2 turns out, the low-speed compression at 14 clicks and the rebound on 25. We tested sag settings as low as 110mm and as high as 100mm. We opted for 105 to keep the chassis more balanced. Too much race sag causes the front end to push at turn-in.
(6) Clutch: The new Brembo hydraulic clutch feels more like a normal clutch than the previous Magura. Best of all, the Brembo clutch uses DOT 5.1 brake fluid instead of the Magura's mineral oil.
JODY'S BOX: MIA
What has happened to the online archives of Jody's Box? I've been a huge fan of his stories since getting my first copy of MXA in 1980 at age 10. I always buy MXA when I can in the UK, but used to enjoy just going online during my lunch break.
We sent this question directly to Jody, who answered thusly: "The boys at MXA's website forwarded your email to me personally because I am the one who told the website to take down all of the old Jody's Box columns. They wanted to keep them up, but I like to have the stories unveiled one at a time in the magazine--and not leave any trace behind me.
"I have received lots of emails from people who want me to put them back up, but it isn't going to happen. I prefer that the stories disappear--that way, the ones I don't like I don't have to think about and the ones that I do like are more exclusive. I understand that this is a hardship in places where it is hard to get MXA on a regular basis.
"There is a simple solution. MXA has a digital version--it is emailed to subscribers at the exact same time that American readers get their paper subscriptions. It can be downloaded to your hard-drive. It has zoom, search, active websites and, best of all, gets to Europe months before the paper versions. And it is cheap. Go back to the home page top rad all about it."
HOUR OF POWER
I bought an hour meter for my CRF250 and mounted it on the left frame spar, but it isn't working. What is the best spot to mount it and is there any thing I am doing wrong?
We mount our hour meters on the right side of the frame (behind the head tube, in front of the gas tank). We remove the gas tank and run the wire down the backbone to the spark plug wire. It is important that you wrap the hour meter's lead wire around the spark plug wire tightly and several times. It gets its juice of the electricity flowing into the enginethat way it only runs when the engine runs.
We have used both two-sided tape, pop rivets and stick-on Velcro to hold it to the frame.
If you have any problems call DR.D at (951) 808-1114 for help.
KX450F: MISSING LINK
I am interested in the linkage system for the KX450F, but I got on the Pro Circuit website and could not find that linkage for KX450F. I was hoping you could tell me where you picked up that linkage
Pro Circuit definitely makes a link for your KX450F. It may not be on their website yet, but if you call (951) 738-8050 they can tell you all about it.
2005 YZ250F: SUSPENSION SETTINGS
I have a 2005 YZ250F. I was wondering what the best suspension settings the MXA test crew found for a 190 pound Intermediate rider.
In 2005 the YZ250F used Kayaba AOSS forks. It stands for Air/Oil Separate System. These were Kayaba versions of Showa's Twin-Chamber forks. We call them Showabas. They're not exact copies of Showa's Twin-Chamber forks, but they're close.
Forks: Set the compression on ten and the rebound on 12. Enjoy.
Shock: We ran our sag at 97mm. In a world that has come to think of 105mm as an acceptable number the YZ250F works much better with a little less sag. We ran the compression on 8 out and the rebound on 10.
These are starting points, you will have to modify them for track conditions.
AMA POINTS AND OTHER THINGS
I find it confusing that Chad Reed is only two points behind Ricky Carmichael with only two wins. I think it would be interesting and informative to break down the points chase and show where points were won or lost, including the points from that illegal gas debacle.
As with any points system, consistency is rewarded more than wins. The difference between winning and finishing second in a race is only three points (25 for first and 22 for second)--and only five points between first and third (25 to 20)--which means that if a rider fails to score any points, like Ricky did when his shock spring broke, he loses 25 points (more accurately 24 because he would get one point for finishing last in the main event). Simple math would tell you that it would take eight wins to get back those 24 points (if Reed finished second every time). The math is 8 X 3 = 24. If Reed was third and Ricky was first it would take less that five wins in a row (because Ricky would gain five points on Reed). The problem for Ricky is that James has been winning as a of latemeaning that Ricky has been getting 22 points and Chad 20which is only a two point gain. So when Chad won and RC got sixth last weekend, that was a 10 point swing for Reed (which erased all of the Ricky's second place finishes versus Chad's thirds). And that is how Reed got so closehe hasn't had a terrible race, while Ricky and James have.
AMA points are paid as follows:
and so on until 20th get one point.
No points were lost in the fuel incident because the AMA rescinded RC's points penalty a few days later.
CHAD REED DEFENDER
I just ingested the May issue, and one thing really jumped out at me. In your top 100 heroes of Supercross, you mentioned a number of riders, including Stewart and RC, but not Chad Reed. You mentioned Reed's mechanic and about 90 industry insiders, that included some of the Team Yamaha staff, but not Reed. I know he's not as flashy and fast as RC and JS, but he has led laps, led the points, won two races, and gutted out that incredible second place ride at Daytona two days after a separated shoulder. I think Reed at least deserves to be mentioned.
We certainly weren't slighting Chad in the May 2006 issue--anymore than Travis Preston, Grant Langston, Ivan Tedesco or a host of other riders that we chose not to include. We did include Team Yamaha's Alan Olson, Keith McCarty and Jim Perry because the story was about people behind the scenes. We added in riders like Carmichael, Stewart, Lewis, Wey, Villopoto, LaRocco, Millsaps, Short, Jimmy Wilson to add a little balance. Additionally, we had a stand-alone Chad Reed interview in the April 2006 issue.
CRF450: HEAD SHAKE AND HANDLING
I have a completely stock 2006 CRF450. Is there anything I can do to calm the steering down when charging sandy straight-a-aways?? As I pick up speed the steering seems to get nervous. I have no other handling problems with the bike (it's actually my favorite bike I've ever owned).
You have several options for calming down head shake:
(1) The quickest and easiest to do is to slide your forks down into the triple clamps. The farther you slide them down, the slacker the head angle. As the head angle slackens, the trail increases. The more trail a bike has the less likely it is to shake. The forks can easily go down until the top of the clamp is even with the threaded-on portion of the fork cap (on many bikes we have actually submerged the forks capbut you shouldn't have to go that far).
(2) While you are sliding your forks down, check your race sag. With you in the saddle, the bike should sag approximately 100mm (when measured from the rear axle to the rear fenderin a line similar to the swingarm stroke). If the race sag is less than 100mmsay 95mm, this keeps the rear end high and steepens the head angle. Check the sag and set it on 100mm.
(3) A Honda shock has high-speed compression damping (the large dial on the top of the shocknot the one with the screw driver slot). Turn it all the way in and count the number of turns (it should be less than two). Then turn it back out 1/8th of a turn more than it was initially. This will allow the rear end to ride lower under acceleration (conversely, turning the high-speed compression adjuster in will make it ride higher). This is not related to race sag.
(4) Your last choice should be a steering stabilizer (like WER or Scotts). They are designed to stop head shakebut are expensive.
I read that you could get three more horsepower out of a CRF450 by using VP racing fuel. I was wondering how much more horsepower you could get out of a 2006 KX250F by using the same gas.
Oxygenated fuel would add approximately 1-1/2 horsepower to a 250F. I'm sure that you also read that it cost $13 a gallon...and it can't be left in your carb for more than three weeks without causing a residue problem. That is no problem if you ride the bike every week...but sitting unused with VP U4 in the float bowl is not good.
JIM O'NEAL'S SHOTGUN
I was trying to figure out what is written on the butt stock of Jim O'Neal's shotgun on page 57 in the May 2006 issue. Did he write that himself or is it doctored? The writing in question is just below the "Bush 04." It says something "rat." What does it say?
It is the date of when Jim's shotgun was cleaned last. He writes the date on the stock to keep track of its regular maintenance.
KX250F: COOLING SYSTEM
I recently purchased a 2004 KXF250. I have installed a Boyesen water pump/oil cover with impeller to aid in cooling. I am thinking of running either Engine Ice or WaterWetter. Which would you recommend ?
We used WaterWetter or Maxima Coolanol on our KX250F (both were recommended by the Pro Circuit team ). Also we changed the 2004 radiator cap (to a 1.6), drilled out the louvered radiator guards and ran the Boyesen impeller.
CRF250: PUMPS, PIPES AND SPRINGS
I read the May issue of MXA (which gave all the smart mods for the CRF250R) and I ordered the TBT insert (couldn't afford the whole carb) and am looking to get some new clutch springs. What brand of clutch springs should I get? Also...would the Boyesen Accelerator pump cover be of any use with the TBT mod? I am also going to be able to get the Yoshimura exhaust at 50% off due to sponsorship (when I get the money). Will this give me the same power increase as the Dr. D singe exhaust system? You have to admit it looks pretty cool. OK...so I asked several questions. Please help me out and I promise to leave you alone until I find myself completely stumped.
Here some quick answers:
Clutch springs: We got stiffer clutch springs from Pro Circuit.
Boyesen QuickShot: We tested every combination of 2005 part for the 2006 CRF250 and we tested the Boyesen QuickShot, the 2005 carb and the TBT carb mods. We felt that the 2005 carb eliminated about 95 percent of the bogging, the TBT mod about 85 percent and the Boyesen Quickshot about 50 percent. We did not put the QuickShot on the 2005 carb or on the TBT carbso we can't tell you if the combination is any better. But, when your bike is jetted perfectly, we don't see any real advantage to the QuickShothowever, on bikes with burbles, hiccup and bogs, the QuickShot is a big help.
Yoshimura pipe: We loved the Yosh RS3 twin-pipe on our 2006, but when we tested the 2006 DR.D single pipe we felt that it worked better than the Yosh. We agree with you that it didn't look anywhere near as cool. In our case, we took everything off of a 2005 (airbox, carb, subframe), so we couldn't mount a twin even if we wanted to.
CRF250: SPARK PLUG CONFUSION
I just bought a 2006 CR250R. The sparkplug that I am supposed to use is an NGK BR9EG-N-8. I went to my local dealer and he didn't have one so I bought a BR9EG instead. Can I use this plug without any problems? What is the difference between these plugs, if any?
The quick answer is that you can run a BR9EG instead of the BR9EG-N-8.
In BR9EG-N-8 the alphanumerics can be translated thus:
The B means that it is 14mm thread size.
The R means it is a resistor type.
The 9 is the heat range (9 is colder than 8).
The E is the thread reach. E represents 19mm.
The G means it is a fine wire nickel alloy electrode.
The N means it has a side electrode.
The 8 (at the end) means it is a wide gap plug (0.8mm).
The BR9EG that you want to use is fine...depending on weather and gas you could also use a BR8EG (a little hotter plug)
CRF450: PUSH COMES TO SHOVE
I recently bought a 2006 CRF450. It is my second, I had an 2003 prior to this one. My 2003 handled great with the stock offset, but on my 2006 the front wheel washes out really easy when exiting a turn. Any ideas to make this better?
Get rid of the stock Dunlop 742 front tire. It doesn't work in the real world.
YZ450F: QUICK SUSPENSION NUMBERS
I have just purchased a leftover 2004 YZ450F. Could you dig up some of your suspension settings for the big Yamaha for me?
The biggest rap against all YZ forks has been bottoming. With each model year Yamaha has lessened the the YZ fork's tendency to clank, but it seems that they were held back by the rubber baby buggy bumper bottoming system of the older model 46mm forks. For 2004 Yamaha went to 48mm forks (with long, conical, male/female, hydraulic bottoming cones). It's old technology, but it worked better than the bumpers of 2003. We turned the compression out to 12 and the rebound to 10.
As for the shock, we liked it, but the difference between one or two clicks was immediately noticeable. That was a good thing--unless we were one or two clicks off. We spent a lot more time making clicker adjustments on the 2004 YZ450F than any other bike that year. When we got it right it was very very good. One click off and it kicked. Depending on your track, set the ride height at 100mm, the rebound on 12 clicks out and the low-speed compression on 12.
Also, we replaced the stock 48-tooth rear sprocket with a taller 47. Why? Although most pros can handle the 48, slower riders and recent two-stroke transplants found that the 47-tooth sprocket allowed them to use second gear for starts, most corners and downshifts. In many cases it eliminated having to shift into third on the exit of turns, which decreased stalling. If you are having trouble finding the right gear, stalling in tight turns or getting a good start--consider a 47.
YZ250F: NUMB HANDS
I own a 2002 YZ250F (I'm hoping to get a new one in 2007) and my fingers go numb after about fifteen minutes on the bike--mostly my throttle hand. I have aftermarket upper clamps with rubber bar mounts and an aluminum throttle tube on TwinWall bars. Am I holding on too tight? Are my bars worn out? My local shop said to fill the bars with liquid filler foam and that all the Pros do it. What should I do?
Unfortunately, we don't think that the problem has anything to do with your bike. You have covered most of the bases (and in scientific testsfilling the bars with construction foam doesn't do anything for vibration and no factory riders do this)although there are heavy lead weights that do a decent job of toning down vibes inside handlebars. The TwinWall bars are probably overkill and you would be a little better with Renthal Fatbars. Again, we don't think that is the root of your problem because you have the same basic bike as thousands of other riders, who don't have your problem (did you check your motor mount bolts?)
We'd be willing to bet that your ulnar nerve, which runs across the palm of your hand, is playing a major role in your problem. We say this because it has happened to factory riders in the past. Additionally, most riders get arm pump, numbness and hand troubles on the clutch sidenot the throttle side.
Here are three things you can try.
(1) Relax your grip. You don't have to hang onto a motorcycle with all your might. Grip the tank with your knees and allow your hands to float on the grips.
(2) Hold the throttle like you would a door knob. Don't grip it with four flat fingers wrapped around it in an even row. Bring your elbow up and slide your hand down the end of the throttle with your thumb running underneath (as close to parallel to the grip as possible)that will take the pressure off your palm. Open and close the throttle with a twist of the wrist, like turning a door knob.
(3) Change gloves. If you use padded palms, switch to unpadded gloves. If you have unpadded gloves switch to padded gloves.
RM250: THE WHOLE BALL OF WAX
I just bought a 2002 RM250, from your experience can you tell me the best gearing? I'm running 13/50 right now, the best carb settings, and the best suspension settings for a 165 lbs. rider. Thanks.
Good luck with your new bike, you will need it for the jetting. We have traditionally had jetting problems with Suzukis, and the 2002 was no different. As much as Suzuki hates to admit it, their bikes need race gas to perform at their best. Without race gas, you will chase a rich, lean, rich scenario with every twist of the throttle. The combination of a Throttle Position Sensor and Power Jet, which were the rage a couple years ago, only confuses efforts to get the RM250 properly jetted.
Here is what we ran in our bike for SoCal's sea-level tracks:
Pilot jet: 45 (48 stock)
Power Jet: 50 (45 stock)
Air screw: 1 1/2 turns
Clip: 4th (3rd stock)
As for the gearing, bikes with light flywheels present some serious gearing problems. The lack of flywheel inertia translates into beaucoup trouble in sand, deep loam and heavy going. Unfortunately, gearing it down aggravates the problem because of the shortness of the torque curve. We tried gearing the 2002 RM down, but shorter gearing only translated into an even shorter powerband.
The Suzuki is at its best on tight tracks and hard dirt. It's best to run this engine tall and use the clutch to compensate when it bogs down.
When it comes to the rear suspension the 2002 RM250 was completely out of balance. The rear of the RM250 felt like it has two feet of suspension travel, while the front fork felt like it is stinkbugged downward. Making matters worse is the minimal compression damping on the rear shock. It gives the rider the false sensation that it is stout enough, but as soon as he powers through a G-out or lands from a big jump, it bottoms out. The quandary is that turning the compression clicker in doesn't stop the bottoming, but it does increase the harshness over smaller bumps.
To get the most out of the 2002 RM250, you will need a stiffer shock spring. What was our best setting?
Spring rate: 5.0 kg/mm (4.8 stock)
Race sag: 98 mm
Lo-compression: 8 clicks
Hi-compression: 1 1/2 turns out (1 stock)
Rebound: 11 clicks (13 stock)
In 2002 Suzuki traded their normal Showa's Kayabas. The major test rider fork complaint was identical to the shock complaint. On the setting where the forks felt best in the small to medium bumps, they bottomed. When the compression clicker was turned in to stop the bottoming, the fluid feel disappeared.
We ran compromised settings for each and every track. But, more often than not we found ourselves with the compression clicker turned all the way in. Not good--and a definite sign that stiffer fork springs are called for.
What was our best setting? For hard-core racing we recommend this set-up:
Spring rate: 0.44kg/mm (0.43 stock)
Oil height: 454cc
Compression: 8 clicks out
Rebound: 14 clicks out
Fork leg height: level
CRF450: SUSPENSION SETTINGS
I just bought an '06 CRF450 and I was wondering what settings you used on the suspension when you did your test of the bike?
The 2006 suspension is firmer on compression than the '05 model, which makes it better overall. It stays a little higher in the stroke and fits a wider variety of riders. That said, MXA test riders have a tried-and-true fix for Showa forks that has worked since 2002. We install stiffer 0.49 kg/mm forks springs and lower the oil height from 385cc to 375cc. We set the compression and rebound on 10 clicks out. With the stiffer fork springs and lower oil height, the fork is plusher over small bumps, stays higher in its stroke on consecutive hits and can handle the big landings. Do it.
The shock is decent. We set the sag at 100mm, low-speed compression on 12, high-speed at 2 turns out and rebound on 10. It was a little kicky over braking bumps (which required a delicate touch with the rebound adjuster).
YZ450F: TARGET PRACTICE
What is the target rider weight and ability level for the 2006 YZ450F's stock suspension?
We called Yamaha's official test rider, Doug Dubach, to get the official answer. Doug said, "The 2006 YZ450F is design for a 180 pound rider that is somewhere between Novice and Intermediate skill levels. But, it isn't that cut-and-dried. Spring-wise the YZ450F suspension will work with riders from 150 pounds to 200 pounds without stretching the preload capability."
TWO-STROKE VERSUS FOUR-STROKE
I want to make the change from two-stroke to four- stroke. I am hesitant due to the fact that I really know nothing about four-strokes or the maintenance they required (compared to the two-stroke. I don't know if I want a 250F or a 450. I currently ride a 2003 RM250 and I weigh 190lbs in street clothes. Which bike would you recommend for me?
We can't tell you what to buy, but since you ask, here is what we think you should buy. If you are intent on getting a four-stroke, and that is the trend, you should get a 450. Since you are coming from a 45-horse RM250, we can't see how you'd be happy to go to a 35- horsepower 250Fand at your weight you have the muscle mass to handle the 50 horses of a 450 (plus the extra 15 pounds).
There is a cost factor involved. Two-strokes, which are still viable in the 450 class because they make decent horsepower with light weight and snappy response, are much cheaper to maintain. They have very few moving parts, so for the price of piston, rings and gasketsyour two-stroke can be brand new. A four-stroke has about 10 times as many moving parts. In a rebuild you can expect to pay five times more for the parts you need to make a four-stroke new. And, if the four-stroke blows up before you rebuild itthe cost ranges from $1700 to $3000 (depending on how much damage occurs). That sounds scary, but most four-strokes don't blow up if they get regular oil, air filter and bolt maintenance (at least not for two to three years).
We would recommend that you get a Honda CRF450 or a Yamaha YZ450F. Not that you couldn't live happily-ever-after with a KTM, Suzuki RM-Z or Kawasaki KX450but, since you are new to four-strokes the YZ and CRF offer more chances to seek help from others ridersjetting, suspension settings and the ability to borrow a part at the trackjust based on the popularity of these two machines.
LOOKING FOR THE RIGHT BAR
Could you tell me what kind of ProTaper bar comes stock on the 2006 Yamaha YZ250F? Supposedly the bike could handle better with 10mm taller handlebars, but I need to know what kind of bend the stock bar is first to be able to tell which taller ProTaper bar to purchase.
Unfortunately, MXA never asked ProTaper the exact name of the stock bend because we changed them on the first ride (initially using spacers under the bar mounts,) but ProTaper did sent us a set of ProTaper "YZ High" bars which were taller than the stockers and had the same bend. Your dealer should be able to get this bar for you.
LONG ANSWER TO A SHORT QUESTION
I've read every word that MXA has ever said about the 2006 YZ450F and Honda CRF450. I would normally just buy the Honda, but this year the blue bike got so many revisions that it seems like the one. Can you please clear up any real world differences between the bikes.
The differences between the YZ450F and Honda CRF450 are very great. The bikes have very different traitsnot necessarily bad traits, but each does things in its own way. Here is a quick list:
(1) Power: Both make 50 horsepower. Honda's style of power is quite old school. It chugs a little more and goes pockity-pock at low rpm. It is more of a thumper and because of this it feels very manageable and, we think, hooks up a little better than many other four-strokes. The Yamaha is a much more modern engine. It has a five-valve Genesis head, 100 percent tungsten counter-balancer and a power delivery that is much smoother. It rolls on nicely and revs cleanly. The simplest comparison is that the CRF450 feels like big XR400 while the YZ450 feels like a 450cc automobile engine.
(2) Handling; The previous Honda's (2002, 2003 and 2004) were bad handling bikesregardless of what people like to think. Over those years, Honda, who was well aware of the front-end shortcoming of the CRF450, produced three completely different frames. In 2005, the frame came around to its' current excellent level. The Honda is a very good bike at turn-in (although a little clanky on the entrance) and superb from center-out. The Yamaha's greatest handling trait is its light weight (not that it weighs any less than the CRF). Thanks to centralization of mass (lowering the radiators, lowering the seat height, lowering the crank height and rotating the rotating mass of the piston back towards the center of gravity), the YZ450 feels 20 pounds lighter than the CRF when leaned into a corner. That said, the YZ450F has some push at center-out (which can be mitigated by better front tire choice and slight chassis adjustments at the forks).
(3) Suspension: No suspension system works until it is set up properly for the rider and track conditionsbut all things being equal the YZ450F's Kayaba SSS forks are better than Showa's Twin-Chamber forks. Again, the CRF450 forks are very good (especially when compared to KTM, Kawasaki and Suzuki--just not to the Yamaha).
ECU'S AND EFI: KISMET
With rumors of EFI 450s for 2007, will this be much better than their carburated predecessors?
Every manufacturer is working of EFImaybe for 2007 and maybe for 2008. Most companies already have an EFI ATV on the market. As for the difference between EFI and carburetion, I expect that as far as ease of jetting goes, power delivery and throttle pick-up with EFI will be betterbut for the average racer, and I mean racer not rider, carburetion is foolproof (once it is right). Most racers ride hard...and ask their carbs to produce fuel on demand, which a carb is very good at because it works on engine vacuum. Racers don't cruise very often, go from sea level to 7000 feet on the same day or want to pay the premium price for untested stuff. Additionally, unless the motocross bikes gets more sensor probes and electronics than the ATV's, there will be a brisk market in hopped-up ECU's to make the EFI work when you change pipes, port the head or open up the airbox.
Please help me! I have my first race in one week. I bought a 2006 YZ450F and love every aspect of it except the front tires won't stick in a corner, either flat of sandy. I ride a lot of sand and intermediate terrain. I heard word of 27mm offset clamps... Does that help? What tire?
It is difficult for us to analyze your problem without actually seeing your personal "big picture." Since you say that you ride on sand and intermediate dirt, we have to wonder what front tire you have on your YZ450F? The stock tires on the YZ450F are a Dunlop 739 front and 756 rear. The 739 is designed for hard terrain. It has short knobs with considerable buttressing and a closed pattern. It is not a good intermediate-to-soft tire because it doesn't have enough tread depth for loose or loamy dirt. As a rule, we run Dunlop 756 front tires on our YZ450F in Intermediate terrain and a Dunlop 773's in full sand. On hard terrain we run about 15 pounds in the front tire, 14 on intermediate terrain and 13 in the sand. Front tires are critical to performance (and front tires vary the most in performance).
Based on track conditions we raise and lower the front fork height (higher up in the clamps will steepen the head angle and make the bike turn sharper, while lower will calm it down at speed and slow down the cornering). This is the most valuable tuning tool that a rider has because it is one of only two ways to change frame geometry on the spot (the other is to change race sagwhich also changes the head angleamong other things).
As far as front offset goeswe do run 27mm front triple clamps on our YZ250F, but do not recommend that offset for the 450. At the moment we are testing 23mm offset for the 450, but have not finished the test cycle and aren't totally convinced (by the way, stock offset is 25mm).
LIFE SUPPORT FOR THE CRF250
In your April 06 issue you rated all the bikes. I have a 2006 CRF250 and was wondering why you came to the conclusion that it blows up with regularity? Is there anything I can do to stop it from happening?
We came to that conclusion based on the fact that we personally know a lot of people who blew them up (and from dealer reports). But it doesn't have to happensince most of the failures were caused by poor maintenance. The most important thing is to watch the engine oil like a hawk. If you let the oil go down by 100cc, it will lose the next 100cc in half the time, and the next 100 cc in half of that time and so on. Low oil height increases engine temp and cause premature wear, galling and destruction of the engine. The CRF250, because of its split engine and tranny oil system, has about half of the engine oil as a YZ250Fand the oil needs to be checked after every ride.
IN OR OUT WITH SHOWA
When turning the clickers on my Showa suspension, which way is in, and which way is out?
"In" is clockwise, "out" is counter-clockwise
SNAIL CAM ADJUSTERS
Why don't the old-style cam adjusters work on today's machines? I still see them on late model trail bikes. Today, I have to put my glasses on, stand on my head to see the hash marks and have a hand full of wrenches for each bike.
The main reason that snail cam-style chain adjusters have fallen out of favor is chain torque. The trail bikes that use the old-style adjusters are low horsepower engines that don't land hard from big jumps (with the throttle on).
BEST BIKE FROM A DECADE AGO
My local AHRMA club has developed a "Decade" class, where any machine 10 years old or older is authorized. I am considering a 1996, 1997 or 1998 KX250. Any suggestions?
The 1996 and 1997 Kawasaki's were very good machines. The '97 and '98 models were exceptionally good. The powerband of choice at the time was low-to-mid and the KX250 was the class leader in this style of power.
The '96 had very soft forks and overly stiff rear suspension (for the time). It defined stinkbug at the time.
The '97's rear suspension was light years better, but the forks were still stinkbug. The engine was awesome, but it had a weak clutch (we ran XR400 clutch springs from Barnett in it). The '97 model had a longer swingarm than the '96 model and this was a big plus to the handling--it put more weight on the front wheel and moved the rider forward. These Kawasaki's were "upright handling" bikes. They liked to be steered through the corners more than leaned over--that was Emig's style. If you had to buy a bike, any brand from 1997, the KX250 would be the best choice since it was the best 250 in 1997.
I own a 2003 CRF450. Currently, I run a Dunlop 756 19" x 120 series rear (110 is stock) and a Dunlop 742front. Further, I have a 22mm offset triple clamp with the forks set in the stock position and rear race sag at 95mm. The bike still understeers. It is bad at turn-in and mid-corner, but fine in high throttle exits. My question is: Would running a 100 series 756 tire offset the understeer, or would the narrower profile cause me other fits?
The 2003 Honda CRF450 had a tendency to wallow in the center of the corner, which required throttle steer to bring the back end around. The normal fix for this, back in 2003, was 20mm offset triple clamps, careful adjustment of fork height and the best possible front tire. Base on your letter, you are on the right track...except for a couple minor things.
(1) The 742 front tire does not help with your understeer. It is a rather vague front tire that was designed for Supercross a few years agoand only works on moist crumbly dirt. It is a tire that we take off if we have any cornering problems.
(2) Your triple clamp choice (22mm) should be fine, but you will need to raise and lower your forks to steepen the head angle to suit the conditions. Too high and it will oversteer. Too low and it will understeer.
(3) The 120 rear was a bad idea and the 100 rear would be an equally bad idea. The 120 profile is very flat on the bottom and tends to resist rolling onto the side knobs (when compared to a 110). This makes the bike stay upright too long into the center of the corner. It also hooks up at low speeds which makes the front tire pushwhich of course aggravates understeer). A 100 rear tire would spell an end to getting a good start on cement because it would be more prone to wheelspin. It just isn't enough rear tire for a 450.
We would recommend that you go back to a 756 front and 756 rear (110), balance your suspension out as much as possible and then focus your cornering tests to fork height changes.
GREAT AND UNITED
I was wondering if you could give me advice or information on motocross schools within the United Kingdom, as I am intrested in motocross but I live in England?
Sorry, but we are Americans and the only thing we know about England is that you turn right at Iceland to get there. Try this website: www.motoxmag.co.uk
RAW METAL AND RUST
What kind of maintenance is required for a pipe such as the Pro Circuit Works pipe? I have read in different places that they corrode if you don't maintain them.
Because the pipes are raw metal--they rust. To stop this, we spray the pipe with lubricating oil (WD-40, Maxima, etc) and then we rub the pipe with a ScotchBrite pad. You have to do this about once a month (or immediately after any mud or rain race). You don't have to do this with plated pipes, but they don't look as cool.
LEFT-OVER 2004 RM-Z250
I was able to buy a leftover 2004 RM-Z250 for the right price and I have never owned a four stroke. Would you be kind enough to dust off your 2004 setup specs?
How much do you want to know? Here is a quick list of 2004 set-up, traits and problems
(1) Heat: The 2004 radiators are smaller than the 2005 radiators. The 2005 model has radiators that are are 40mm longer and have a 17.8 percent larger core area . We swapped the stock 1.1 radiator cap on the 2004 for a 1.6.
(2) Vibration: The RM-Z/KX-F engine doesn't use a counter-balancer. It vibrates.
(3) Handlebars: The stock bars were steel.
(4) Clutch perch: There is no on-the-fly clutch adjuster?
(5) Tires: The stock tires were Bridgestone's 601 and 602 tires. Luckily, they should be long gone from your bike.
(6) Suspension: It is unbalanced.
Forks: The old school Kayaba units handle big hits and little bumps without any major complaint, but we had to do something to them to alleviate the stinkbug stance. The rear is high and front is low. Our remedial fix was to run the forks 5mm above the top triple clamp and run 105mm (and sometimes as much as 110mm) of race sag in the rear shock. We ran the forks as stiff as we could stand them on compression (approximately six clicks out) and the shock as soft as we could go (approximately 15 out).
Shock: In our opinion the stock shock set-up is way off the mark. It is so over-damped that the rear end transfer loads to the front of the chassis--which in turns overloads the forks--often resulting in major head shake. Serious racers should invest in Pro Circuit's works linkage. It helps balance the bike out and soften the rear suspension. Unfortunately the RM-Z250 shock does not have high-speed compression adjustment--because our first move would have been to turn the dial out.
(7) Gearbox: Third and fourth gear were weak in 2004 (proven by the fact that they were shot-peened in 2005 to make them stronger). The gearing benefited by adding one tooth to the rear sprocket.
(8) Valve float: The RM-Z/KX-F engines valve problems were caused by valve float. Stiffer valve springs can fix this problem,.
(9) Cam buckets: We ate through a set of buckets (where the cam rubs against them).
THE FABLED BLIND SIDE BEARING PULLER
I am pretty sure that I read in MXA about where to find a blind side bearing puller and I can not seem to find that particular issue. If you could help me I would be very grateful.
Try GG Mechanica at (888) 700-2382. They offer an excellent Beta bearing puller.
HONDA OFFSET QUESTION
RG3 has different offsets on their clamps and I would like to know the best set up for my 2005 CRF450. I have Race Tech suspension and am very happy with the overall handling, but i feel like I need to get over the bars farther to get in the right position on the bike. What should I do?
If you owned a 2002 or 2003 CRF450 we would recommend 20mm offset. On the 2004 we ran 22mm offset, but Honda changed the offset (at the axle dropout) and the frame geometry in 2005--to mimic the specs that everyone was using. The only difference between a 2005 and 2006 frame is that the 06 engine is dropped 5mm in the front, but this only provides a minor improvement in overall handling at turn-in.
You sound like you know that your problem is one of set-up and ergos more than frame geometry. Before you buy handlebars mounts that will allow you to move your bars forward (which is cheaper than an all-new top clamp), just rotate them up-and-forward and ride (remembering that they will be taller and swept a little weird). That should give you a quick feel for having the bars farther forward. Many times for many riders, farther forward isn't better, but slightly taller is.
DEAD IN THE WATER
Last weekend my brand-new KX250F refused to start after practice. It had worked fine before that, but nothing I did would make it start (including pushing it)? Where should I starting looking?
That's simple. We suffered the same fate with our KX250F. For 2006 Kawasaki changed the cam chain stopper plate. The new stamped steel plate has little winglets that the 04-'05 stopper didn't have. On our bike, the winglet broke off and fell down into the ignition, where the small metal piece shorted out the ignition. That is where we'd look first. We replaced the 2006 stopper plate with the 2005 version (the part number is 13271-0169).
SINK OR SWIM
MXA is always talking about stiffer valve springs, new valve seats and valve float, but I don't understand what the big deal is. So what? If the bike won't rev, shouldn't the rider just shift sooner?
True, but if you have to baby your bike on top, you won't be getting all of its performance. The big danger of valve float isn't that the bike won't rev, it's that the valve and piston clearance will be reduced by the lag time. If the valves float they can strike the piston. This is catastrophic.
KAWASAKI KX450F HELP
I bought my 2006 Kawasaki KX450F before I got the issue of MXA with the test in it. I wish I had waited because I have the same complaints that your test riders had: (1) Poor gear ratios. (2) Wallowing rear suspension. (3) Bottoming that leaves rubber under my rear fender. Can you help me fix it?
Yes and no. We have tried swapping the stock 50-tooth rear sprocket for a taller 47, 48 and 49. For big tracks we had our best luck with a 48, but were always leery about using first gear in the slow corners--because it required us to make a critical shift across neutral on the exit of the turn. For tight tracks we stuck with the 50 and and even had good luck with a 51.
As for the rear suspension; if you are big and fast, try a 5.7 shock spring (with the rebound slowed to four clicks out). The 5.7 will help the compression damping and hold the rear end up to eliminate the wallowing, but hurt the rebound. If you are light or slow, the 5.7 solution will make the rear suspension too stiff. We have had good luck with the Pro Circuit shock linkage (like the one they use on the KX250, KX250F and KX125). It lowers the rear end, which is a good thing, and stiffens the first 220mm of the shock's stroke. Our best luck has been with a revlaved shock or Ohlins KX450 shock and the Pro Circuit link (which is what is on all the Kawasaki race bikes).
OLD WIVES TALE
When I load my bikes on my trailer the only way I have of keeping them down tight is to compress the front forks. I hate doing this because it obviously it kills the springs. Got any ideas on what to do?
Year ago, when fork spring metallurgy was in its infancy, fork springs would sack out from over use, but not in the last 15 years. Think of it this way, if your fork springs can take hitting the ground at 50 mph with a 200-pound rider on them, how could being pulled down a few inches by tie-downs hurt them? Cinch them down tight. It will not hurt them.
ALL HAIL ATHENA
I have an 2006 Honda CRF450 and would like information on big-bore packages you have tested and prefer. I ride the Over-40 class in motocross, but still go pretty fast. Thanks for your help.
Given our druthers, the MXA wrecking crew would choose the Athena 488 kit. The complete kit retails for $787.95. Call (909) 608-0082 for info.
2002 YZ250F SETTINGS
I recently got a 2002 YZ250F. I was wondering what the best suspension settings the MXA test crew found for a 185 pound rider.
Here are our recommendations for the 2002 YZ250F:
(1) Geared it down. We added one tooth to the rear sprocket.
(2) On the shock we ran the race sag at 97mm, the high-speed compression on 1 1/4 turns, the low-speed at 7 clicks out and the rebound at 11 clicks out.
(3) For the forks we ran 14 clicks out of the compression, 12 clicks out on the rebound and slid the forks down until 5mm of fork tubes extended above the triple clamps.
CORRODING BEFORE YOUR EYES
The foam on my Oakley goggles rots away before I'm ready to buy new goggles. The rest of the goggle is fine, but the face foam disintegrates. Any solutions?
Yes, after every race weekend dip your goggles in a bucket of clean water. The clean water will remove the dirt and sweat that are detrimental to the foam.
GO BIG OR GO HOME
This year the Honda CRF250 comes with a 40mm Keihin carb. Last year it had a 37mm carb. Why don't all bikes go to big carbs?
In an age where bigger is better, a big carb is not the always the best solution. A large venturi flows more air and fuel, but at a slower velocity. This means that the engine has to turn over faster to maintain sufficient air flow to keep the fuel flowing. A smaller venturi carb flows less fuel and air, but at a higher velocity. The rule of thumb is that a big carb is best for high horsepower at a higher rpm and a smaller carb is best for snappier throttle response and better jetting at lower rpm. As for the 2006 Honda CRF250, we think that the 40mm Keihin is too big, which is why we run a 2005 carb (37mm) on our CRF250. A cheaper solution is a TBT carb stuffer, which brings the 2006's 40mm carb down to 38mm. Call TBT at (509) 941-7716. It retails for $79.95.
Suzuki Motorcycle tests