My son's kymco super9 50cc won't start we have changed the piston and rings as these broke scooter wouldn't go over 20mph changed gear oil was running for a couple of hours then went to pull off on it and it died and won't start there is a spark and fuel in the spark plug the carb is sucking just not sure what to do had to buy a battery as the kick start broke but it worked fine off this please help .