shifting clunk

[Chris Krok]

I think the shifting "clunk" is a by-product of a multi-plate clutch. I haven't been inside my clutch yet, but here's the theory: You can only apply pressure to the outermost plates, so the inner ones just float on the shaft/basket. When you leave the bike running in neutral with the clutch engaged, the whole package is spinning. When you squeeze the clutch, the outermost plates disengage, but there is nothing to force the inner ones to do so. So, some of the friction and drive plates can stick together, causing the output shaft to keep spinning. When you actually shift into gear, the output shaft is forced to stop, breaking the clutch plates apart. Therein lies the clunk. Since the clutch is wet, there will be some drag even when the plates are disengaged. So, you get less clunk with lighter weight oil, or after the oil has warmed up. If anyone has any corrections, please post! Thanks. Chris -- Dr. J. Christopher Krok Project Engineer, Adaptive Wall Wind Tunnel Graduate Aeronautical Laboratories, California Institute of Technology MS 205-45 Phone: 626.395.4794 Pasadena, CA 91125 Fax: 626.449.2677