this bike used to run perfectly. it sat in my garage for the last 2 years without me touching anything. i drained the old gas, and put in new gas, and sprayed some carb cleaner in the carb and it fired up. it backfires a whole lot whenever i turn the throttle. It doesn't idle or run when the choke is off. like i said, when i do turn the throttle, it backfires a lot. can someone please tell me the problem and how to fix it???