Clutch chatter is an audible grinding/chattering noise when the clutch is being engaged and the bike is starting to move. This is especially noticeable in sidecar applications.
Clutch chatter is something Indian tried to deal with which usually proved unsuccessful. Indian at 1 point tried self centering clutch release bearings which was a failure and didn't solve the problem.
We have been doing numerous studies and experiments with alternative clutch parts and come up with what has been a successful combination that we developed for racing and heavy duty sidecar applications (which certainly works with ease on a stock bike). We completely redesigned the clutch pressure plates and then made them from billet aluminum and hard anodized them for long life. This assembly captures the springs on both plates ensuring they remain positively located at all times even under heavy sidecar use. Not only is this assembly lighter (under 1/2 the weight of the original) but it is also more rigid which greatly reduces the chances of clutch chatter.
springs cockeyed in original assembly
springs positively captured in Kiwi assembly
Aluminum vs steel friction plates.