I think all your problems stem from the the rear float needle not seating properly, or the rear float level being too high. The seat should be as narrow as possible, giving a high seat pressure. Try lapping the needle and seat with Brasso or similar metal polish. Banging in exhaust is from an overly rich mixture firing in the hot exhaust. Once a float chamber starts to flood it does so continuously by siphon action. Try lowering the chamber by rotating the carb.