so a couple weeks ago my muffler fell off while i was riding, and i couldn't find it anywhere on my backtrack. the motor wouldnt start without one to i ordered the stock muffler from bikeberry.com, i used two screws and washers to screw the muffler into the motor , but the screws come loose after 10 minutes of riding because my pedals hit it while im trying to ride and start up. any ideas? is the stock muffler too big? this didn't happen with the other one.