so now im here, i bought a new racing carburator for my 80 cc it came with a new throttle cable and 5 jets 60-80 i started with the 80 and ended up on the 60 jet it was fine... it was the one that made her go fast well after about ten min of riding at almost top speed i hear a knocking sound. it will stay running but i have not tested it to see if it will engage and actually ride im worried i blew my engine but my research has me to believe i have a piston problem should i buy a new one?