OK so i have a eBay frame mounted engine with 44t exhaust. it ran great and never gave me troubles. So i let me buddy ride the bike and he was gone for about an hour. He came pushing it back and said it stopped running. I asked him what he did and he had no idea. Then i asked him if he was going AS FAST AS HE COULD DOWN HILL and he thought for 2 seconds and said yes. Idiot. NOW it vibrates like crazy, but everything seems like it is tight and working properly. I have checked everything but internal motor stuff. OHH and the exhaust sounds more muffled than before. Any ideas yall?