MXA RACE TEST: The New 2009 Kawasaki KX250F; Suspension Settings, Jetting Specs, Likes & Dislikes, Plus Much More

MXA TEST OF THE 2009 KAWASAKI KX250F


There are several key ingredients that are necessary for a competitive 250cc four-stroke motocross bike. Element number one is the engine-?the heart and soul of the machine. Without a powerful 250cc four-stroke engine, the overall package of the race bike would be severely compromised. Next is the suspension. The forks and shock must work in unison with the rider’s weight and skill level. The suspension is instrumental in helping the frame’s geometry maximize the bike’s handling. Make no mistake about it; a great handling machine makes a world of difference, especially when coupled with a powerful engine. There are other factors intrinsic in a great bike-?strong brakes, a bulletproof clutch, seamless shifting and comfortable ergonomics?and all of these parts, and their relationship to each other, contribute to making a bike good, fair or poor.

The MXA wrecking crew wanted to do the math on the 2009 Kawasaki KX250F. Here is the equation as we see it.

Q: WHERE DID THE KX250F FINISH IN LAST YEAR’S MXA SHOOTOUT?

A: It won. For the last two years (2007-2008) Kawasaki has been the best of the bunch when it comes to 250 four-stroke motocross bikes. It achieved this honor in spite of what many people saw as shortcomings: the 2008 KX250F didn’t produce the most horsepower (that honor went to the KTM 250SXF), handle the best (the nod went to the RM-Z250), or have the best suspension (the YZ250F took the cake). So, how did it win two shootouts in a row? The KX250F had the best overall package. Yes, the KTM made more power, but it was listless power. Yes, the RM-Z250 handled better, but it was seriously undersprung. Yes, the YZ250F had the best suspension, but it lacked a potent punch. As a result, the MXA test crew recognized the KX250F’s prowess as a race bike. Not blessed with the most of anything, it had the best combination of everything. That said, the 2009 model had a lot to live up to.

Q: WHAT’S NEW ON THE 2009 KX250F ENGINE?

A: Marketing departments always claim that their new models are substantially…well, new. Kawasaki’s did too, and they weren’t lying. Here are the biggest changes to the 2009 KX250F.

Crank: Borrowing technology from Kawasaki’s race team, the lower side of the crankshaft has 40-percent more weight than last year (to increase mid-to-high rpm performance and provide smoother power delivery).
Intakes: The intake ports on the cylinder head are much straighter and smoother, which increases intake efficiency across the rev range and improves performance at all rpm. Kawasaki also beefed up the thickness of the intake valve heads (from 0.75mm to 1.0mm), which improves strength and longevity. The intake valves are still made of titanium, but Kawasaki used a different grade of titanium for more strength.

Watercooling: The water jacket was moved from the side of the cylinder to the front for better cooling performance and more consistent flow. To aid in cooling, the width of the radiators was increased by 6.4mm (increasing coolant capacity by six percent), and the radiator louver design was changed from three large fins to four smaller fins (at an increased angle).

Lubrication: Engine oil has been decreased from 1.5 liters to 1 liter (which reduces weight and mechanical loss).

Cam chain: The torque on the cam chain tensioner was reduced from 44 newtons to 31 newtons (reducing mechanical loss by 30 percent). We know what you are thinking, what is a newton? Have no fear, 31 newtons equals 3.1 kilograms.

Oil screen: The KX250F receives the same scavenge pump screen that the KX450F uses (a single wide screen as well as a barrel tube screen).

Q: WHAT’S NEW ON THE 2009 KX250F FIVE-SPEED TRANSMISSION?

A: Kawasaki listened to MXA’s complaint regarding the fussy shifting on the 2008 KX250F. In response, they changed from a gear-driven shifting system to a ratchet-driven system. The space between the gear shafts was also increased by 1mm to accommodate stronger gears. It’s better, but not great.

Q: WHAT’S NEW ON THE 2009 KX250F’S ALUMINUM FRAME?

A: For the first time since 2006, the KX250F frame has been changed. Kawasaki shaved 2.2 pounds off the frame by making the aluminum spars 6mm narrower. The head tube was also slimmed, and the swingarm pivot point was raised 3mm (to increase chain torque). The subframe was also put on a diet and is 1.1 pounds lighter than in 2008. This was achieved by using larger diameter tubing and one bracket instead of two for the exhaust and rear fender.

 As for the swingarm, Kawasaki moved to a tapered “D” shape design on the swingarm. The new swingarm is 5mm taller, 2mm narrower and weighs 0.9 pounds less. A different cross-brace design was also utilized. By adding chain torque and stiffening the initial part of the rising rate curve, the 2009 KX250F rear suspension stays higher under small loads. While the 2009 KX450F and KX250F don’t share the same swingarm (the KX450F’s swingarm is longer), they do share the same pivot point height increase.

Q: WHAT’S NEW ON THE 2009 KX250F SUSPENSION?

A: Kawasaki stuck with the Showa shock and 47mm Showa forks, but there were several minor changes.

(1) The fork tubes of the forks are now titanium-coated to reduce friction and improve action, while the stanchion tubes are Kashima-coated.

(2) The shape of the outer stanchion tubes has been changed from a tapered tube to a consistent thickness throughout the tube’s length. The constant-wall tube is more rigid than the tapered tube.

(3) A new upper triple clamp has its offset changed from 24.5mm to 23.5mm (to increase trail).

(4) The fork’s damping settings have been changed, there is 4cc less oil in the forks, and the fork guards have been given the same wraparound treatment that KTM has been using (to offer greater protection).

(5) In the shock department, the cylinder body layout has been changed to allow for easier adjustment, the shock shaft has been Kashima-coated, and the damping has been changed to ride higher in the initial part of the stroke.

Q: WHAT ELSE HAS BEEN MODIFIED FOR 2009?

A: Here is the list: the 2009 KX250F received a larger resin skid plate, new chain guide (more compact with a thicker wear pad), 50mm wide footpegs (up from 48mm), slimmer seat, one-piece shrouds, one-piece number plates, new fork guards and redesigned engine guards.

Kawasaki also offers a Monster Energy KX250F edition, which comes with green hubs, black plastic and Monster Energy graphics (this version retails for $200 extra).

Q: WHAT DID KAWASAKI HOPE TO ACHIEVE WITH THE 2009 POWERBAND?

A: Before we tell you how the 2009 KX250F engine is performance-wise, we feel obligated to tell you the direction that Kawasaki wanted to take. Their focus was on maintaining the same potent mid-to-high powerband that the KX250F has become known for. Yet, they also wanted to improve on their barely evident low-end grunt. How do you gain low-end without losing top? Kawasaki’s engineers added 40 percent more weight to the bottom of the crank’s central mass. The swinging pendulum effect is a surefire way to increase torque.

Q: HOW DOES THE 2009 KAWASAKI KX250F ENGINE RUN?

A: Did Kawasaki accomplish their goal of improving the overall spread of power on the KX250F? Yes. The 2009 engine is remarkably better. It is beefier from low-to-mid, stronger from mid-to-top, and actually gained some over-rev (once you get the crank’s moment of inertia swinging, it likes to keep going).

ÿÿ Last year, the KX250F was at its strongest from 7000 rpm to 13,000 rpm. The 2009 model is stronger than the 2008 KX250F at every point on the dyno curve. Not only is it one horsepower better from 6800 rpm to 8000 and 1/2-horse better from 8000 to 9500, but it’s up to three horsepower better from 10,500 to sign-off. That’s a serious improvement! The 2009 engine has a more usable spread of power through its complete range. Every test rider, from Novice to Pro, raved about the manageability and performance of the engine.

Q: DOES THE KX250F STILL HAVE THE BEST ENGINE IN THE 250 FOUR-STROKE CLASS?

A: Engines come in all styles. Some are mid-and-up, some are low-to-mid and others are top-end only. Each engine characteristic has its minion of devoted followers. The MXA wrecking crew must admit that we tend to favor mid-and-up powerbands-?especially on 250cc four-strokes. We think they are the epitome of gun-and-run motocross. They hit hard and rev far. Those are the exact traits that we admired so much on previous KX250F engines. Guess what? We love what Kawasaki has done for 2009. The same brutish powerband as before, but with more on the bottom and the top.

Interestingly enough, the 2009 Kawasaki KX250F is still the 250 four-stroke with the least peak horsepower of the Big Five. The KX250F maxes out at 35.5 horsepower, that’s 1.1 horsepower less than the YZ250F (36.4) and 3.1 horsepower less than the KTM 250SXF (38.6).

Q: HOW CAN THE BIKE WITH THE LEAST HORSEPOWER BE ANY GOOD?

A: Motocross isn’t all about peak horsepower (drag racing is). Motocross is about producing the right amount of power, at the right time, and in the right spot to thrust machine and rider forward. Horsepower is important, but in the overall picture, it is just one factor of many. Kawasaki may not make the most power, but it makes the bike with the best race engine.

Q: WHAT ARE THE FLAWS OF THE 2009 KX250F?

A: We have three major complaints.

Handling: Kawasaki knew that they had a handling problem and they switched the offset on the 2009 KX250F’s triple clamps from 24.5mm down to 23.5mm to try to fix it. Sorry, that incremental change didn’t help much. The front-end still had a tendency to stand up in the center of flat corners and push on the exit. By sliding the forks up in the clamps, fiddling with race sag and turning in the low-speed compression, it is possible to reduce the steering quandary…but we never eliminated it. This has been a Kawasaki handling trait for a decade.

Our solution in 2009 was the same as in 2008. Swap the stock triple clamps for 22mm offset clamps. This is what all of the factory Kawasaki riders run on their bikes. With more trail, the handling became precise and the front-end felt planted through the entire turn. We were also able to run 100mm of sag and return the fork leg height to 5mm (down from 9mm).

Gearing: Heavens to Betsy, the KX250F suffers from improper gearing. The stock 13/48 combo was too tall for every test rider, including AMA National Pros. The gap between second and third gear is massive. We opted for a 49-tooth rear sprocket. Surprise! Just like last year, the additional tooth closed the gap between gears and worked well in conjunction with the powerband.

Jetting: Our first few test rides were spent trying to figure out the lackluster jetting. The 39mm Keihin carburetor’s settings were off substantially. The bike was rich off idle and under heavy acceleration. Kawasaki switched from a 170 mainjet in ?08 to a richer 182. We dropped the mainjet, raised the pilot and turned the fuel screw in. Unless you are riding around on frozen tundra or in a cave thousands of feet below sea level, you will most likely need to lean out the carburetor.

Q: WHAT DID WE DO TO THE STOCK KX250F JETTING?

A: The stock mainjet was too rich for most conditions. We dropped the mainjet, richened the pilot jet and leaned out the fuel screw. If you ride in hot conditions or at high altitude, we recommend that you stick with the stock pilot jet.

Main: 180 (182)
Pilot: 42 (40)
Needle: NHJT
Leak jet: 55
Clip position: Fourth from top
Fuel screw: Two turns out (2-1/8 stock)
Notes: The NHJT needle is new for 2009. The taper has a gradual progression, unlike the 2008 needle, which is stepped.

Q: HOW GOOD IS THE SHOWA SUSPENSION ON THE KX250F?

A: For 2009, Kawasaki didn’t make any radical changes to the Showa forks or shock, and since most MXA test riders were happy with the actuation, spring rates and valving on last year’s KX250F, we liked this year’s as well. Not surprisingly, test riders gave the KX250F suspension a seal of approval. It doesn’t have the fine tuning ability or plushness of the Kayaba SSS suspension, but it still works well.

ÿÿ We found that Intermediate and Pro level riders, as well as those over 175 pounds, bottomed out on
compression clicks quickly and needed to jump up on spring rates (both front and rear).

Q: WHAT WAS OUR BEST FORK SETTING?

A: For hardcore racing we recommend this fork setup:

Spring rate: 0.44 kg/mm
Oil height: 306cc
Compression: 9 clicks out
Rebound: 13 clicks out (11 out stock)
Fork leg height: 5mm up
Notes: If you have to go less than six clicks out on compression, you should step up to the next stiffest spring rate.

Q: WHAT WAS OUR BEST SHOCK SETTING?

A: For hardcore racing we recommend this shock setup:

Spring rate: 5.4 kg/mm
Race sag: 100mm
High-compression: 1-1/4 turns out (2-1/4 out)
Low-compression: 9 clicks out (12 out stock)
Rebound: 10 clicks out (12 out stock)
Notes: We think that the KX250F works best with the low-speed compression turned in, while using the high-speed to adjust the ride height at speed.

Q: WHAT DID WE HATE?

A: The hate list:

(1) Handling. The KX250F is one set of 22mm offset triple clamps short of being a very good handling bike. In stock trim, the bike stands up in the center of the corner and pushes from center-out. Do yourself a favor and invest in 22mm offset clamps.

(2) Gearing. Apparently Kawasaki overstocked their warehouse with 48-tooth sprockets. Too bad, because the KX250F needs a 49.

(3) Rear axle nut. Kawasaki is the only manufacturer that uses a cotter pin as a safety precaution on their rear axle. It may make Kawasaki’s lawyers happy, but it drove us crazy. We recommend that you purchase a Honda axle nut and swap it out.

(4) Graphics. On the showroom floor, the KX250F graphics look nice. After an hour of riding, we forgot what the graphics looked like because they were crumpled up in a heap somewhere out on the track.

ÿÿ (5) Muffler. Surprisingly, our 2009 KX250F passed the AMA’s new 94dB sound test (conducted at 5000 rpm), but on the track it was far-and-away the loudest of all the 250Fs we have sound tested. We immediately asked Kawasaki if they failed to install muffler packing. Yes, it’s that loud.

(6) Chain guide. Kudos to Kawasaki for making the rubber block in the chain guide 2mm thicker. The way we figure it, that 2mm should add up to about six more laps before the chain eats through the block and the aluminum bracket and reaches thin air.

Q: WHAT DID WE LIKE?

A: The like list:

(1) Engine. Kawasaki’s engineers managed to get more low-end grunt without sacrificing top-end power. Houdini couldn’t pull off that kind of magic act.

(2) Appearance. The 2009 KX250F looks fast right out of the box. The black rims, two-tone color scheme, one-piece plastic and reshaped side panels were a hit among MXA test riders. Just beware of the black plastic and rims, as they quickly show their age.

(3) Handlebars. We have a soft spot in our hearts for 7/8-inch aluminum handlebars, like the ones found on the KX250F. They perform well and are cheaper to replace than their oversized brethren.

(4) Weight. Kawasaki was able to shave 3.3 pounds off the KX250F. In the highly competitive 250 four-stroke class, where weight is a major factor, cutting excess fat off the bike is important.ÿ

(5) Transmission. Last year the KX250F tranny was on our hate list, but by switching from a gear-driven system to a ratchet-driven system, the shifting improved, but isn’t amazing.

Q: WHAT DO WE REALLY THINK?

A: In the past, specifically in 2007 and 2008, the MXA test crew was willing to overlook the KX250F’s weak points (handling, shifting and gearing) because of its strong points (powerband, ergos and suspension). The question at hand is whether the 2009 KX250F’s added juice and improved shifting are enough to keep the KX on top. We think so, but we know that Kawasaki could have made our choice easier with different fork offset, one tooth more on the rear, more durable shroud graphics, a quieter muffler and one less cotter key.

Read the 2009 250F shootout now

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