bbr offers a big bore exhaust the head and mid pipe are a little larger than the one for the stock 50s, sano also has a bigbore exhaust theres a couple more out there but i cant think of them i like the bbr fit and finish is always great and soon you can get it in black
Big Gun Exhaust currently has a big bore version of their pipe. this pipe works well on motors up to 95cc. They are building a new pipe for my 117SE motor but I am not sure when it will be available to buy. We'll be running it this weekend at the 4 stroke nationals so I should be able to get you some good feed back on this set up.