Regarding the clutch problem Have you checked the lever on the h/bar if it has been replaced by a pattern part the hole fitting to cable fitting may not be the correct distance then not allowing a full pull for the cluth to disengage also cable inner could have a boken strand or being rusty then check the cable run so there are no tight bends everything should be smooth in layout, all said I take it you do not have a clutch body and plate problem..
Just an Idea to try cheers Dave.