I built this monstrosity two years ago because I thought it would be cool... And it is. It has a 3.5 horse tecumseh engine. I don't know the exact cc of it but the modern 3.5 horse tecumseh for a mini bike application is 156 cc. which is over 3 times what most engine powered bicycles have, most are just converted using kits. mine was converted using bad judgment. The fastest I've gone was 38 miles an hour according to one of those radar trailers the police set up that tells you your speed. This isn't even a bmx bike. It was a girls 20in mountain bike, it still has the cassette on the back wheel. also that bit of heat shield isn't there to keep me from getting horrible 3rd degree burns but to keep my shirt from getting sucked into the exposed spinning fly wheel that's covered in sharp teeth right where my spine is! well hey, I do call it a death machine for a reason. I might do a YouTube video on it because that's where I got a lot of the info I needed to build it.