You should have loosened one screw when removing the stock engine and unhooking the cable. Sounds like it was either screwed up when you got it or you unhooked more that you should have, maybe trying to get more speed from the stocker? I'll take a picture later and post it here, but I think it has been done and with a little research using the google search on the home page! Try it and be sure to choose the OldMiniBikes search not the web! Good luck and if all else fails I'll post the pics.................