How can the cam chain tensioner cause a problem with the crank? If the tensioner fails, it usually causes the chain to come loose or break, changing cam timing and bending valves. Top end suffers, not bottom end.
What are the symptoms? What parts need to be changed? Did the bike quit suddenly?
I'll bet the chain broke because the tensioner wasn't adjusted properly.
The 904 conversion shouldn't cause any problems with the tensioner.
