Uni-Trac Linkage Maintenance

The Kawasaki EX500’s Uni-Trac suspension is well designed, but suffers from one serious cost-cutting measure. Instead of using needle bearings at the pivot points (as on its more expensive models), Kawasaki decided to utilize a sleeve and bushing bearing arrangement to save costs. As seen in the diagram above, the sleeve is simply a metal tube that rotates within a pressed-in bushing made of a composite material. If not well greased and maintained, the sleeve can corrode and the bushing can erode, creating either friction or resulting in a large amount of freeplay. These are both a serious no-nos and should be remedied.

Freeplay/Friction Inspection:

To see if your motorcycle has too much freeplay, place your motorcycle on its centerstand and firmly grasp the rear wheel. Try to move it up and down. If there is too much play in your pivot points, the wheel will travel up and down a few millimeters without moving the shock absorber. Indeed, you may even be able to observe certain pivot points of your suspension move up and down as you move the rear wheel.

To check for excess friction, it is best to remove the rear shock and move the entire suspension through its travel. It should move freely and not bind or squeak. Excess friction can also cause your rear suspension to squeak while you sit on your motorcycle and bounce up and down. If this is the case, you need not remove the rear shock, for this indicates that your pivot points are in need of lubrication.

Disassembly and Lubrication:

Disassemble your Uni-Trac suspension, remove the sleeves and clean all parts in solvent. Inspect each sleeve for excessive wear or scoring. Lack of lubrication will usually result in a black patch on these sleeves, generally indicating that friction has bonded bushing material onto the sleeve. Pitting and rust on the sleeves can also occur as well if your pivot points were not well lubricated or if moisture had been able to work its way inside. Good, re-useable sleeves will be perfectly round and have a flat, shiny surface. Those that cannot be cleaned to this standard should be replaced. If it becomes necessary to replace a sleeve, it is also a good idea to replace its mating bushing, as corrosion and lack of lubrication will have most likely damaged that mating bushing. Prior to reassembly, insert each sleeve within its mating bushing and, after greasing, try to move it about up and down. Excessive freeplay can be seen this way and parts should be replaced if guilty. Reassemble using a quality, heavy grease and torque to factory settings. Inspect again for freeplay. Due to the limitations of the sleeve and bushing design, it may be impossible to eliminate 100% of the up and down freeplay. The objective is to reduce it to a negligible amount.

Long-Term Solution:

If you grow tired of completely disassembling your suspension linkage, a solution is to install zerk-type grease fittings. To do so, purchase some of these brass fittings at an auto supply store. These grease fittings come in both metric and English sizes, and the package should tell you what size tap is needed to cut the threads in your rocker arm.