First, drain the tank of old gasoline. Fill up with fresh fuel. Go find your self a can of Sea Foam carb and injector cleaner. NAPA or Walmart usually carries this in their automotive section. Pour the Sea Foam into the tank and let the engine run and warm up. This will allow the Sea Foam to work itself into the carbs. Turn the bike off and let it sit for a day. Run the engine again and repeat procedure. Change the fuel filter and this should hopefully solve your carb problem. If not, you are looking at pulling the carb rack and cleaning the carbs. Good luck and keep us posted on your progress Don