With Paul's latest info I'm gonna guess it's in the clutch assembly
somewhere. Possibly pressure plate, possibly clutch disc, possibly gland
nut freezing up the needle bearings in the gland nut, possibly loose
flywheel. Paul says it stops when depressing the clutch. Gotta be in the
pressure plate, clutch flywheel assembly. Though one possibility you gotta
think about is the crankshaft wobbling around because of a bad main or worn
case. Grab the crank pulley and push and pull and see if you have any
detectable play. Shouldn't be any.
Sammie
