Life for manufacturers used to be easier when it came to selling motocross four-strokes. At one time both Yamaha and Honda dominated the market. But now every color has a 450F and they're all great. It was rumored that Kawasaki postponed the release of its 450 for one year after it could have produced it. It wanted the bike to be right, and the extra year paid off. Despite being the last Japanese brand to enter the 450 class, Kawasaki has made, and continues to make, a big impression. The KX450F has had few problems and a great deal of success. Many of its triumphs have been earned in motocross/supercross (James Stewart, Michael Byrne and Tim Ferry) and arenacross (Darcy Lange and Josh Demuth), but the model has also earned a Hare & Hound title (Destry Abbott) and a WORCS championship (Ricky Dietrich). Clearly the basic package is complete. The changes for 2008 are what we'd call thorough fine-tuning, but the difference in performance is significant and surely sufficient to keep the KX-F battling with the best in the class.
Even though aluminum frames have had a very positive effect on the sport, the technology is still evolving with the primary focus on torsional rigidity. The challenge is to engineer enough twist into the frame to aid turning and traction. Kawi moved the engine mounts 10mm farther from the engine to allow more flex in the chassis. Even with the black "Diamond Like Coating" on the fork legs, the suspension wasn't perfect in 2007, so the inside surfaces of the upper fork tubes and shock reservoir gained a low-friction Kashima coating for '08. The overall suspension settings are slightly stiffer as well, and an effort was made to further balance suspension action front to rear.
The changes to the crank and flywheel have worked magic on the power delivery.
In 2007 the suspension performance was challenged by an engine with such massive pull that the rear end had to cope with that load and bumps. For '08 the engine gets pork chop- shaped crank webs and a heavier flywheel to smooth the delivery and aid traction without reducing overall boost. A variety of small changes to the rod material, oil pump, shift drum and the ignition enhance reliability, add confidence in the shifting and allow easier starting when hot. And then, of course, there are those black rims to spark up the look.
The attention to detail lavished on the engine is obvious as soon as the bike starts. The KX lights easily, has all but perfect jetting and crisp and immediate response. It's also apparent that the bike is loud. Kawasaki was quick to point out that the thumper passes sound. We suspect that the ignition is engineered to make the bike meet AMA regs at the test rpm, but the bike is much too raucous in higher rpm ranges.
Smoother power makes corner exits less dramatic, but there is still ample boost.
If you tune out the sound, you can start to enjoy the KX just fine. The changes to the crank and flywheel have worked magic on the power delivery. The engine rolls on super smooth out of turns, grip and traction are abundant and reliable and the rider can choose the moment for the jump to light speed. Once the throttle is opened past the halfway mark, the track gets gobbled up at an amazing rate. The pull is never violent like the bike is trying to tear your arms off, but you end up really hauling on the straight parts of the track. Adding flywheel effect has merely calmed the power. Ample snap to clear jumps right out of turns is still on tap. We never considered lower gearing, but a few riders could conceive of wanting a tooth or two less on the rear sprocket.
A few riders noticed a reluctance to transfer from second to third gear in a hurry, while others wondered why you would bother using second gear. Shifting earlier and being sure of the shift ended most complaints.