It is a two smoke and simple, four stroke kits are pricier and more complicated. There are aftermarket pipes, carbs etc. available on the net. The stock pipe can be modified for more noise/power. It is available on the web or direct from distributor in Poco(EHBC Holdings 1608 Broadway). They have two options in stock a 48cc or 66 cc. With some mechanical ability it will fit many applications. Still fussing with my application, hope to be riding it to Bruces this weekend if time permits. Check out zoombicycles.com seems to be the website associated with EHBC, they also carry electric bikes. $162 and change for the big block, taxes in.