Brian

Sounds like a timing issue. Youl get more opinions on this but I think you need to check timing and I would go so far as to say if your chain has jumped a tooth it could be out, what, 18 degrees, I think, so that could cause damage. Don't want to cause a panic attack but better to be safe. There is lots in the archives about timing. I use the bubble method (don't want to get into a pi**ing contest here. ) Was the old bolt the right length (washer the right thickness too) and the threads gone, or what. The bolt should have threaded in EASY then come up hard & tighten down then.

Steve