In this article, I will briefly acquaint you with the Kawasaki/Suzuki 65cc Original Equipment (OE) suspension layout, tuning tips, and modifications. As a suspension tuner and motocross aficionado, I have observed many discussions of the KX/RM65 suspension. There are numerous message boards full of ambiguous suspension mods and specs for this bike.
The front forks on the KX/RM65 have been outdated by several decades, but they can be adjusted for certain riding conditions. The damper rod forks found on the KX/RM65 are outdated as they create an overly progressive damping curve (they are too soft initially and too harsh during rapid fork movement). The rebound adjuster on the front forks can be used to adjust for some head toss and difficult cornering. Head shake may occur due to excessive or insufficient rebound damping. This can be fixed by turning the adjuster in two click increments and testing. The rebound adjust can also help with cornering issues. If the bike washes out in the corners, turn the rebound adjuster clockwise in two-click increments. If the bike doesn’t lift out of corners fast enough, turn the rebound adjuster in two-click increments. The front of the bike can also be lowered by moving the forks up in the triple clamps. This can help cornering, but can cause head shake.
KX/RM65 models are equipped with a rebuildable rear shock that is mounted to a modern linkage system. This system increases the workload of the shock absorbers as the rear suspension compresses further to the bottom. A starting point for tuning your rear shock is to set the stroke sag to 70-75mm but not to exceed the static sag by 25mm. If it is not feasible to meet both conditions, a different rate shock spring may be required. The rebound adjuster can help stability and rear traction. If the rear end of the bike drifts to the sides or lifts up, it may be due to excessive or insufficient rebound damping. To resolve this, turn the rebound adjuster in one turn increments and test. Rear traction is often lost when there is too much rebound damping and this can be fixed by turning the rebound adjuster counterclockwise one turn.
The suspension performance of the original KX/RM65 is not enough for the most competitive motocross riders. There are two effective popular tuning services available for KX/RM65 forks. An emulator valve can be fitted which offers a less progressive and more predictable feel at the front of the bike. This mod is sold as a “bolt-on kit” but is not effective if installed that way. Additional shock rod modifications are needed to properly tune the rebound damping. A cartridge system is also available for the forks that can be installed after the lower fork legs have been machined. This cartridge system can be tuned by replacing shims and through rebound and compression adjustments. The oe KX/RM65 rear shock has a lot of potential and can be adjusted with a revalving service. The suspension on the KX/RM65 may initially be mediocre, but with the right suspension tune-up services, it can become a very competitive 65cc dirt bike.