[squirrel_hunter]

Hard to be sure from remote diagnostics, but I would suspect an air leak at some point. If you have balanced the carbs are you sure that you've blanked off the balance connectors fully and there are no splits or leaks there? Next I'd be looking towards the exhaust, are all the joins solid, if you are still on the original down pipes the front to mid section likes to corrode. Also what is the condition of the end can, I had some popping where the exhaust packing had burned through?

Whats it like while riding?