KX450R Suspension Review
Spring selection is great for riders 170 to 190 pounds. 160 and below should consider a 5.2 rear and .46 front spring. Over 200 pounds will need at least a 5.8 rear and .48 front springs.
Kawasaki uses the same KYB components that Yamaha uses, yet valves them completely differently. The KX is valved to ride higher in the stroke under low an mid speed damping, and then blows through and bottoms on more aggressive impacts. So slower riders complain that the bike is stiff and harsh while more aggressive riders find the bike bottoms too much particularly the rear. Kawasaki continues to use this valving strategy for several years.
We find that the same valving concepts that we use on the Yamaha, also works well on the Kawasaki with only slight tweaking.
2003 and 2004 KX 250 Suspension Review
Confused at best - Downright scary at worst.
REAR SHOCK
It may be surprising that I would review both bikes in the same breath since they are different years, different fork internals, and different valving front and rear. The reason is the rear shock is so glaringly bad for both years that it makes the major complaint for both bikes the same. The rear shock does not respond to sharp bumps because the compression damping is too stiff on the edges. The more hard packed the track, the sharper the bump, or the higher the speed, the worse the shock/bike will feel. Because it does not respond to the bumps, the rear deflects and kicks up making the tire leave the ground. Additionally, because the back kicks up, the front goes down and the bike goes into the stink bug position which promotes head shake. At high speeds the rear kicking up / deflecting combined with the front end head shake makes for quite the unstable ride.
Interesting Kawasaki changed the rear valving slightly for 04 in an apparent attempt to relieve high speed compression damping. The result failed because even though the shock may be a hair better, the forks are softer at low shaft speeds and thus fall more easily into the head shake position. This makes the 04 even less stable than the 03.
FRONT FORKS
Kawasaki seems to have set the same objective for fork performance for both years because both the 03 and 04 forks are too soft on the low speeds and too harsh on the high speeds; but for different reasons. The 03 uses a cartridge pop off valve like the YZ forks but they did not use enough valves and let them open too far which prevents enough low speed damping from occurring. The pressure can not rise in the lower cartridge until a relatively high shaft speed at which point they put in too much compression at the foot valve to compensate for the lack of low speed damping. So they go from too little, to too much, damping as the shaft speed changes. They must have realized their mistake for 04 because they deleted the cartridge valves but this time they removed too much low speed damping by making a 2 stage foot valve stack at the compression adjuster. Again to compensate for too little low speed damping they over shot the high speed by using an old (and already failed) bladder design. Most informed shops were removing bladders in the past and will surely contiue.
The end result is the same; the front end bottoms from a drop off, rides low and promotes head shake, yet it still deflects off of sharp edge high speed edges on the track or trail.
FORK FIX
No big deal and the results are amazingly good. KX and many RM's have used this style of fork & cartridge size since 1999. We have lots of experience with this design and dial in the bottoming resistance and eliminate the harshness by carefully tuning the cartridge valves, mid speed, and foot valves. There is nothing wrong with the basic design of these components.
SHOCK FIX
The majority of the shock's problem is an area that other shops do not address, so I will not elaborate here. Trust me that as bad as the forks are, the majority of the rider complaints actually originate in the shock. Many people can not believe that their fork problems were more than 50% caused by the shock. They do become believers after our extensive tuning fundamentals are applied to their shock.
Please give me a call to discuss how I can help your bike or to determine which springs we should use.