MXA’S USED MOTOCROSS BIKE GUIDE: HOW TO SETUP YOUR 2010 KAWASAKI KX450F

On May 30, 2013 Last updated Feb 17, 2018

This is the 2010 Kawasaki KX450F the way the MXA test crew raced it. As a rule, we don’t go for exotic or expensive mods, but if push comes to shove, we will seek competent help (no matter how much it costs). Use MXA‘s mods as a guide.

Plastics: 2010 Kawasaki has the weakest plastics of any manufacturer. The shrouds crack almost immediately. We replaced the stock units with stronger and thicker UFO plastic. UFO sells a kit that includes a front fender, rear fender, radiator shrouds and side panels. To purchase the $145.99 kit, visit www.ufoplasticusa.com or call (815) 756-9400.

Chain guide: In a few hours of riding, the chain guide shows serious signs of wear. If the rubber wear pad isn’t constantly replaced, the chain will eat through the chainguide frame. We replaced the stocker with a durable T.M. Designworks chain guide and chain slider to prevent the chain from wearing into the swingarm. To order the $179.95 kit (which also includes a roller), visit www.tmdesignworks.com or call (541) 535-1612.

Throttle tube: Getting the vulcanized stock grip off the KX450F throttle tube is nearly impossible. So rather than hack up the tube and our fingers, we opted to replace the stock part with an aluminum throttle tube. They cost about $60.

Clutch: The clutch lasts longer than on previous KX450F models (thanks to new friction plates), but the springs are too soft. We installed stiffer $69.95 Pro Circuit clutch springs. For more information, visit www.procircuit.com or call (951) 738-8050.

Radiator cap: Antifreeze seems to evaporate in the KX450F faster than spit in the Gobi Desert. Get rid of the low-pressure 1.1 radiator cap and install a high-pressure 1.6 or 1.8 radiator cap.

Gearing: The five-speed KX450F gearbox is just a modestly refined version of the original four-speed tranny with a fifth gear added on. We have always geared the KX450F down to close up the gaps between the gears, but thanks to the added horsepower that the 2010 engine produces, we were able to run the stock gearing. We did switch to a Renthal 50-tooth sprocket, countershaft sprocket and Renthal R1 works chain.

Rear axle nut: Kawasaki’s lawyers must believe that rear axle nuts fly off like geese going south for the winter. Every year, the KX450F rear axle comes with a cotter pin. We removed the stock axle nut and cotter pin and replaced them with a self-locking CRF450 nut.

Front brake: It takes serious pucker power to slow down the obese KX450F. We drop-kicked the stock brake pads and spongy front brake hose for Galfer units. These changes made an immediate impact on stopping power. Oversize rotors are the way to go. Visit www.galferusa.com or call (805) 988-2900 to order.

Forks: Kawasaki installed stiffer fork springs between 2009 and 2010 (from 0.46 to 0.47 kg/mm), smoothed out the damping and Kashima-coated the inner tubes. The overall fork setup on the 48mm Kayaba AOSS (Air Oil Separate System) forks was vastly improved with these changes. For hardcore racing these are MXA’s recommended 2010 Kawasaki KX450F fork settings:
   Spring rate: 0.47 kg/mm
   Oil height: 340cc
   Compression: 10 clicks out
   Rebound: 10 clicks out
   Fork leg height: 5mm up
   Notes: The chassis is very sensitive to fork height. As a rule, we ran the forks up in the clamps until we got oversteer, then slid them down two millimeters.

Shock: In an effort to end the reputation it had for wallowing, Kawasaki’s engineers built an all-new rising rate linkage (bellcrank and link arms) and upped the shock spring rate from 5.3 to 5.5 kg/mm. We preferred to run a longer Pro Circuit link to reduce wallowing. For hardcore racing this is MXA’s recommended 2010 KX450F shock settings (for the stock set-up).
   Spring rate: 5.5 kg/mm
   Race sag: 100mm
   Hi-compression: 1 turn out
   Lo-compression: 8 clicks
   Rebound: 8 clicks
   Notes: The 2010 KX450F is very sensitive to balance between the front and rear. The longer Pro Circuit link lowered the seat height and stiffened the initial part of shock’s stroke to stop it from moving around under acceleration.

What we didn’t like: We never like everything about any bike and the 2010 KX450F was no different.
    (1) Shifting. This isn’t an A+ shifter. It’s more like a B-. That means you are going to have to be careful when shifting under a load.
   (2) Gearbox. It’s really the old four-speed gearbox with a fifth gear tacked on. It is wide ratio.
   (3) Plastic. The front fender has been beefed up, but the rest of the plastic parts are flimsy (especially the fork guards).
   (4) Rear brake pedal. If you want to run the rear brake pedal low, you have to hacksaw off some of the plunger’s threaded rod.
   (5) Clutch. It’s better, thanks to new friction plates, but it needs stiffer clutch springs to live.
   (6) Weight. This thing is a brick. It weighs ten pounds more than a 2010 CRF450. Shockingly, it weighs more than the electric start KTM 450SXF.
    (7) Sound. The AMA sound limit was higher in 2010 than it is now, and under those 4500 rpm testing standards the KX450F could pass sound test, but once in motion (above 4500 rpm) it was loud…very loud.