<HTML>i had this same problem with my bi-turboi have actualy had two so far heres my stroy:i got a bi-turbo the 2 piece one (pipe and chamber) i put it on it was loud as hell as loud as it is with out a muffler i called the place where i got it from and they said they had sold me the wrong type of bi-turbo the they have gave me was the one for the big bore 70cc kit this is probably what u have i exchanged it for the one piece pipe and it is just as loud as the stock muffler but a lot faster glad to help need any more info mail me i servce mine and everything</HTML>