79 GS850 intermittent chattering when clutching

[RandyRex]

Think I might have done some internal damage, as I'd been riding my bike while my clutch was giving intermittent travel, due to collapse of the thrust bearing, little rollers were flying around behind the basket, partially blocking travel of the rod. Basically, I spent some "stupid time" half-clutching it, and dropping it into gear too many times. Now, I have another intermittent problem, chattering when clutching but only when clutching, wondering if the bevel gear is a bastard to change? I checked in behind the boot, U-joints seem tight as does the entire prop shaft assy, although there does seem to be some excessive free play/lash in the rotation of the rear wheel though the entire prop shaft assy itself seems to be tight. Going to do an oil change in the AM and will look for shavings/chunks, but as it's only occurring when I clutch, and the noise seems to center around the left front footpeg, I'm hoping to avoid cracking the case open, at this point. Any guesses as to what would be a likely culprit for failure from "neutral dropping", for lack of a more "regal-sounding" whitewashing? And, is changing the bevel gear as bad as I'm guessing? Swing-arm removal? I'm guessing either the bevel gear (which I see as preferable) or internal trans damage. The intermittent nature of these things always baffle my dumbass ... =D