Malcolm Smith Racing Hard Parts Collection’s dome washer is a replacement for the part found on current Beta, Husqvarna, KTM and other European 4-strokes. This small part can cause untold grief. It starts with some slight seepage from a little rubber O-ring behind the countershaft sprocket and progressively leads to the destruction of an entire bottom end (don’t ask us how we know).
The OEM thrust washer is made of mildly heat treated material. When you tighten the countershaft bolt, it takes the washer well beyond its elastic limit and permanently deforms. The first symptom of a problem is slight seepage from the case.
The flattened washer can’t maintain the thrust pressure necessary to keep the sprocket tight on the splined shaft. That leads to two different failures. First, the O-ring is allowed enough clearance to start seeping. Worse the splined shaft and sprocket are allowed to more freely pound in each direction as the torque of power versus compression reverses itself.
Eventually torque wins and the countershaft has to be replaced… to the tune of $700 in labor costs alone. It only takes .010″ of clearance (.25mm) to allow seepage, which is your warning sign.
Made of heat-treated tool steel, the Malcolm Smith dome washer can handle two to three times the pre-load force without reaching its elastic limit and without over-stressing the mating components. This solves the O-ring leakage problem as well as extending the life of both the countershaft and sprocket splines.
For more information: http://msracing.com/index.php/default/ktm-hus-countershaft-washer.html