Look for a worn pilot bushing, and/or deteriorated motor mounts. If the flywheel surface is smooth and doesn't show cracks or heat checks, use a random orbit sander and some 40 or 80 grit sandpaper to break the glaze on the disc contact area. Chattering on clutch engagement is often caused by broken or damaged motor mounts.
Jerry

"It is better to be silent and be thought a fool than to speak and eliminate all doubt!" - Abraham Lincoln
Cringe and wail in fear, Eloi- - - - -we Morlocks are on the hunt!
There is nothing noble in being superior to your fellow man; true nobility is being superior to your former self. - Ernest Hemingway
Love your enemies and drive 'em nuts!