The Yamaha 2009 YZ450F; Suspension Settings, Jetting Specs, Likes & Dislikes, Plus Much More

May 28, 2009
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INSIDE MXA’S 2009 YAMAHA YZ450F TEST

   For 2009, Yamaha is playing it close to the vest. Given the fragility of the marketplace and the pressure on price, Yamaha took the safe-and-sane approach to 2009 model revisions.

   Safe side: Yamaha didn’t jump feet first into the fuel-injection fire. Their engineers were happy with the balance achieved with the trusty Keihin FCR carb and decided to leave the experimenting to the other guys.

   Sane side: Yamaha knew that it would be foolhardy to mess with their award-winning Kayaba SSS suspension?so they didn’t.

   So what did they change on the 2009 YZ450F? Surprisingly, Yamaha decided to take a more scientific approach to product development (as opposed to a marketing blitz). That means that there is very little snap, crackle and pop to the new model. Most of the development took place under the hood where it can’t be seen. Yamaha eschewed the sizzle to work on the steak. Is that going to be enough?

Q: WHAT DID YAMAHA CHANGE ON THE 2009 YZ450F ENGINE?

A: Before we expose the 2009 changes, it is important that we take a look back to the mods that Yamaha did on the 2008 model. Here is the 2008 list and the box score.

   Muffler. In 2008 Yamaha’s engineers debuted their semi-mechanical waffle-cone muffler. What a blunder. No matter what anyone tells you, giving up five horsepower in the midrange is not a plus.

   Head pipe. To compensate for the shorty muffler, Yamaha increased the size of the 2008 YZ450F’s head pipe from 41.3mm to 45.0mm. This wasn’t a performance mod as much as an attempt to get back the volume that the bizarre muffler lost.

   Camshaft. In 2008, Yamaha altered the event angle of both the intake and exhaust cams to 100 degrees. We switched back to the 105-degree exhaust cam from the 2006 YZ450F. It increases the midrange hit and provides a broader spread of power.

   Cylinder head: The 2008 cylinder head was cast with straighter intake tracts to improve fuel flow. This was a good idea.

   Piston: The 2008 piston was new, but it wasn’t a performance part mod. The tolerances were tightened to cut down on piston rock.

Q: WHY ARE WE REHASHING THE 2008 ENGINE MODS?

A: That’s simple. The 2008 engine changes are the only mods that the 2009 engine is going to get. To us, the 2009 YZ450F engine is akin to dating twins. If you loved your 2008 engine, you will feel equal affection for the 2009 version (especially since you can’t tell them apart).

Q: WHAT DID YAMAHA CHANGE FOR 2009?

A: Nine things. Some important. Some not. None of them on the engine or suspension. What follows is a list of the changes and explanations for why Yamaha made the moves.

Q: WHY DID THEY CHANGE THE 2009 IGNITION STATOR PLATE?

A: To stop ignition failures. Historically, Yamaha mounted their stators directly to the engine cases (typically with three bolts). On the YZ450F, Yamaha reversed the ignition and mounted the stator to the ignition cover instead of the center cases. Unfortunately, this flexier mounting position fed more vibration into the stator plate, causing cracked wires in the coil windings. MXA experienced this problem first hand. For 2009, Yamaha added a fourth bolt to the stator plate to fight vibration and keep the windings intact.

Q: WHY DID THEY CHANGE THE 2009 SHIFT FORKS?

A: We like to think that it was because the MXA wrecking crew constantly whined about stiff shifting and missed upshifts from second to third. Actually, it was because a lot of people whined about the same things. To lessen the problem, the first and third shift forks have had their shafts increased by 4mm. The longer shift fork shaft is more stable (because it inserts 4mm deeper into the engine cases). The first and third shift forks handle shifts from second to third and third to fourth respectively. These shift forks will not work on the 2008 model (unless you change to 2009 cases).

Q: WHY DID THEY CHANGE THE 2009 TOP TRIPLE CLAMP?

A: More handlebar mounting choices. The new top clamps allows for four different bar positions, as opposed to two positions on the 2008 model. What are the new handlebar positions? Standard (which is 5mm farther back than the 2008 bar clamps), 10mm back from standard, 10mm forward and 20mm forward. You cannot duplicate your 2008 stock position with any of the 2009 settings, but you can circle the wagons around it. The stock 2009 bar mount position is with the bar clamps in the rear hole and the eccentric bar mounts swiveled forward.

Q: WHY DID YAMAHA GO TO A BIGGER REAR AXLE?

A: To keep up with the Joneses. By increasing the rear axle size from 22mm to 25mm, the horizontal rigidity of the swingarm is increased (more about that to follow) and the bigger axle is lighter than the small axle.

   If you own spare wheels for your 2008 YZ450F, they will not fit on the 2009 model. But, they can be made to fit by two methods:

   (1) You can use the old 22mm axle and axle blocks in the new swingarm, but you will need to jerryrig a 25mm to 22mm sleeve for the brake caliper bracket and add an extra washer to the axle to take up length.

   (2) If you have aftermarket hubs, like Talon wheels, you can change the two 22mm bearings to new bearings with an inside diameter of 25mm. You will also have to change the wheel spacers and the inner axle tube.

Q: WHY DID YAMAHA REDESIGN THE 2009 SWINGARM?

A: For two reasons:

   (1) To revise the rigidity balance.

   (2) To save weight.

Q: WHAT IS RIGIDITY BALANCE AND WHY SHOULD YOU CARE?

A: “Rigidity balance” is Yamaha’s fancy term for swingarm flex. There are three kinds of flex in a swingarm:

   (1) Vertical flex. Vertical flex refers to the amount of movement the swingarm exhibits in an up-and-down motion.

   (2) Horizontal flex. Looking from the rear of the bike, horizontal flex would be viewed as movement of the swingarm from side to side.

   (3) Twist flex. Since a swingarm is composed of two very long aluminum arms, it is possible for one arm to move up while the other arm moves down. Or, at the very least, one arm to move more than the other arm.

Q: HOW MUCH FLEX DID YAMAHA ELIMINATE?

A: In truth, Yamaha was more interested in feeding in more vertical and twist flex than decreasing it. By our calculations, based on raw data supplied by Yamaha, the 2009 Yamaha swingarm is four percent less rigid vertically and five percent less rigid in twist. Conversely, it is eight percent more rigid horizontally.

Q: WHY ARE MORE VERTICAL AND TWIST FLEX A GOOD THING?

A: A motorcycle is a dynamic vehicle. It doesn’t move through time and space like a brick, but instead flows, bends and molds itself to the terrain. Yamaha’s engineers felt that more vertical flex would help the rear wheel stay hooked up (remember, we aren’t talking about rear wheel movement, but rather about the actual bending of metal). Additionally, given the YZ450F’s reputation as a poor cornering machine, the increase in twisting flex should allow the YZ450F to bend itself into corners with more side load before fighting back (a reaction that exhibits itself as the bike’s tendency to stand up in the center of the corner). Horizontal rigidity is increased for 2009 to keep the wheels aligned under a load.

Q: HOW MUCH LIGHTER IS THE 2009 SWINGARM?

A: Would you be impressed if we told you that it is 350 grams lighter? Probably not. What if we told you that there are 28.3 grams in an ounce and 350 grams is the equivalent of 12.3 ounces? That means that the 2009 Yamaha swingarm is three-quarters of a pound lighter than last year.

   Yamaha achieved this amazing weight savings by hydroforming the 2009 swingarm. In hydroforming, water pressure is used to expand cold aluminum (from the inside) into a swingarm-shaped die. When you combine Yamaha’s hydroformed swingarm with its new low-rider shock linkage mounts, the unsprung weight savings are impressive.

Q: WHY SHOULD YOU CARE ABOUT THE SWINGARM’S RIGIDITY AND WEIGHT?

A: Most MXA test riders don’t feel that a four percent reduction in rigidity on any individual part of the bike is going to be noticed by the vast majority of riders. But, and this is the big but, Yamaha has done a lot more than just throw a lot of yaw, pitch and roll jargon around. Yamaha has put its technology where its mouth is.

   Here is a quick explanation of why even a rider, with Novocain injections in his derriere, should be able to feel Yamaha’s rigidity improvements. Yamaha’s engineers designed the new swingarm to be more forgiving, not only in bumps, but also when subject to the kind of forces that are exerted when the chassis is forced into a corner or through the whoops. The flexier swingarm is a positive step, but one that maybe only a professional test rider would notice, which is why Yamaha didn’t stop there. To help the new swingarm do its job, Yamaha knocked 12 ounces off of the unsprung weight. That is a really big deal! Unsprung weight is the mass that hangs below the springs (fork legs, hubs, brake caliper, rotors, spokes, rims, swingarm, linkage, tires, tubes and rim locks). Unsprung weight is connected to the ground more than the parts above it, because when you hit a bump, unsprung components compress into the chassis to absorb the impact. Unsprung weight works negatively on the suspension.

   Yamaha’s 12-ounce weight savings is a nice touch, but wait, there’s more. The new rear hub is 265 grams lighter than the 2008 hub. When you add that 265 gram savings to the swingarm’s 350 gram diet, the result is a one-pound, five-ounce reduction in unsprung weight. That’s phenomenal!
 
Q: CAN A RIDER FEEL THE REDUCTION IN UNSPRUNG WEIGHT?

A: Yes. The lower the unsprung weight, the quicker the suspension reacts to bumps. The improvement is most significant over repetitious, high-frequency bumps (like braking and acceleration bumps). Why? The more weight you load on the wheels, the more the shock absorber has to struggle to bring the mass to a stop. As the damper struggles with the weight, the suspension packs, the wheels kick and the bike becomes unstable. Shaving unsprung weight lessens the suspension’s work load.

   It’s said that a one pound reduction in unsprung weight is equal to a six pound reduction in sprung weight. Thus, Yamaha’s 1.3 pound weight savings is the equivalent of saving 7.8 pounds on the whole bike.

Q: WHY DID YAMAHA MOVE THE SHOCK LINKAGE MOUNTS UNDER THE SWINGARM?

A: We already spilled the beans in the paragraphs above. They did it to simplify swingarm construction in an effort to save weight. What we didn’t tell you is that even though the shock linkage is totally different (mounting, dimensions and parts), it is identical in rising rate to the 2008 shock linkage.

Q: IS THE 2009 YZ450F FASTER THAN THE 2008 YZ450F?
    
A: No. It makes the exact same amount of horsepower and torque. It is not only not faster than the 2008 YZ450F, it isn’t a very fast 450 when compared to the other brands. The low-end throttle response is dead, listless and flat. Yes, it is easy to use, but it is not a powerband worthy of a motorcycle sold as a race bike. That said, if you aren’t racing the Nationals, trying to qualify for one of the Motor Home Conventions (Ponca, Loretta’s or World Mini) or using it for hill climbs, it’s a fun bike to ride. It doesn’t scare you. It’s a pussycat of a 450 engine.

Q: HOW CAN YOU MAKE THE 2009 YZ450F FASTER?

A: There are two simple choices:

   (1) Gear it down. The quickest way to perk up the corked-up low-end transition is to add a 50-tooth rear sprocket. This is a decent fix that condenses the gear ratios and perks up the gap between second and third gears.

   (2) Buy an exhaust system. Any aftermarket exhaust pipe (expensive full system or inexpensive slip-on) will add jolt to the YZ450F. How much jolt? At least five horsepower?which is nothing to sneeze at.

Q: HOW IS THE 2009 YAMAHA YZ450F JETTING?
   
A: We had no problems with YZ450F jetting last year and thus we cannot logically have any problems this year. No changes to the engine means no problems. The stock jetting is as follows:

   Main: 160
   Pilot: 45
   Needle: NFLR
   Clip position: Third from top
   Fuel screw: 2-3/8 turns
   Leak jet: 55
   Notes: If you run an aftermarket exhaust pipe, swap the stock 160 mainjet for a 165 and raise the needle one clip position. If you want to be more exact in your jetting, you can swap the stock NFLR needle for the NFPR needle (it was stock in 2006). It is a half clip richer.

Q: WHAT WERE OUR BEST FORK SETTINGS?
 
A: These are very good forks. Kayaba is sitting pretty with Yamaha’s SSS forks. We tested with a wide range of skill levels and there was always a clicker setting that worked for everyone from Pro to Vet. For hard core racing, these are MXA’s recommended 2009 Yamaha YZ450F fork settings:

 
   Spring rate: 0.47 kg/mm
   Oil height: 350cc
   Compression: 12 clicks out
   Rebound: 12 clicks out
   Fork leg height: 5mm up
   Notes: The stock oil height is 350cc, but if you feel that the forks are too soft in the second half of the stroke, add 5cc of oil to each leg. Kayaba’s SSS forks are very sensitive to oil height changes and 5cc makes a big difference.
 
Q: WHAT WAS OUR BEST SHOCK SETTING?

A: Yamaha was very smart not to change the rising rate, because the existing rate is spot-on. For hard core racing, these are MXA’s recommended 2009 YZ450F shock settings:

  
   Spring rate: 5.5 kg/mm
   Race sag: 100mm
   High-compression: 1-1/2 turns out
   Low-compression: 11 clicks out
   Rebound: Ten clicks out (12 clicks stock)
   Notes: Riders who weigh over 200 pounds should consider stepping up to a 5.7 shock spring. On the high-speed compression, make small (about 1/8th turn) adjustments to the dial to adjust the attitude of the chassis at speed. Yamaha’s high-speed compression clicker is very sensitive.

Q: DID YAMAHA FIX THE HANDLING?

A: We’d love to say yes, but we can’t. We think that the changes Yamaha made to the swingarm’s rigidity balance and to the unsprung weight are steps forward. It is just that these baby steps don’t make a major difference in the YZ450F’s tendency to push in the center of corners. We are willing to give Yamaha props for their more resilient frame and lighter feel, but this is still a troubled chassis. It isn’t settled in flat turns and is not comparable to a CRF450 or RM-Z450 from turn-in to the center-out.

Q: WHAT DID WE HATE?

A: The hate list:

   (1) Cornering. For the umpteenth year Yamaha slapped some Band-Aids on the chassis, but this frame needs a tourniquet.

   (2) Muffler. Putting this muffler on a 450cc race bike is like John Force sticking a Briggs-and-Stratton engine in his Funny Car. A race bike should roll off the showroom floor ready to race. Yes, we know that many racers buy aftermarket exhausts, but on most brands that is an optional choice. On the Yamaha, it is a must-do.

   (3) Tires. We don’t like the Dunlop 742FA front tire, especially when combined with the ultra-wide 120/80-19 rear tire. Most MXA test riders prefer the 110/90-19 rear mixed with a Dunlop 745 or 756 front. This tire combo is quicker in roll and has less tendency to push on the entrance of turns.

   (4) Brakes. The YZ450F’s brakes are consistent and predictable, but they aren’t powerful.

Q: WHAT DID WE LIKE?

A: The like list:

   (1) Keihin carb. This may sound like blasphemy, but we like carburetors. We understand them, have the tools to work on them and don’t see any reason to change a perfectly good carb for a complicated fuel injection system. After all, if the jetting is fine, what’s the point?

   (2) Unsprung weight. Yamaha saved 1-1/2 pounds in 2007, two pounds in 2008 and 1-1/2 pounds in 2009. That’s a program that pays noticeable dividends.

   (3) Shock spring. The YZ450F has the only titanium shock spring on the showroom floors. And in 2009, it will be the only Yamaha with a Ti spring (the YZ250F is returning to steel).

   (4) Clutch lever. We like the new lever for four reasons: First, the reach is adjustable across a 10mm range. Second, the lever itself is shorter and stronger. Third, the casting thickness of the perch has been beefed up to stop the lever from wiggling up and down as it gets worn in. Finally, the quick adjust has fewer parts and is easier to work on.

   (5) Inline adjusters. Both the hot start cable and the throttle cable have inline adjusters to allow slack to be removed.

   (6) Brake hose clamp. DR.D probably won’t be happy to see that Yamaha copied their aluminum front brake hose clamp, but most YZ450F owners will be. It saves 32 grams.

   (7) Gold-plated chain. Okay, it isn’t really coated with gold, but the gold-like zinc coating is a step up in corrosion resistance.

   (8) Seat cover. Last year’s seat cover had a sand-paper-like gripper material on the top. The 2009 seat has a textured weave pattern to provide grip.

   (9) Rear hub. The new hub is not only lighter, but uses three small bearings instead of two large bearings to support the hub.

   (10) Reliability. We never have valve issues with Yamaha’s five-valve YZ450F head. Although we try to service our test engines at 40 hours, we think the Yamaha top-end is good for 100 hours.

Q: WHAT DO WE REALLY THINK?

A: There are two schools of thought in the world of motorcycle development: (1) Motocross bikes should be built for the average rider, who is better served by smooth, manageable and pleasant powerbands. (2) Motocross bikes are race bikes, not play bikes, and the manufacturers should build the most powerful bikes possible to serve the intended purpose. The Yamaha YZ450F is for the former, not the latter.

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