I'm having some issues with a newly rebuilt Bultaco Alpina clutch(#187). It has a new pushrod, ball bearing, mushroom, basket, hub, plates and steels, springs and throwout bearing. Clutch engages and disengages fine when I adjust it on the bench. But, when I start it and put it in gear I get a terrible squealing and it lurches. It sounds like a bearing trying to seize. I've changed out the throwout bearing and it still happens. Anyone else have this problem? 

Edited December 14, 20214 yr by Sluggo
Added modle #

Have you tried setting off down a slope or giving it a push in neutral then without using the clutch, pop it in gear.

Ride around for a few minutes, warm it up, using the clutch lever, then see if it'll disengage smoothly ?

Might have to use the brakes against the clutch.

Probably not as simple as that though !

Probably not the cause, but did you soak the clutch plates in gearbox oil 24hrs before assembly?