[zimmy]

Todd:

If the carbs backfire up through the carb, then it may be that you have too much overlap in the cam. If they are backfiring out of the pipes, then you probably have some minor air leaks in the exhaust system (slip fit pipes, etc) or it is running a bit lean. Both will contribute to the backfiring. Mine has both and it sounds like World War Three when I get off it!