when i was a kid i put a 750cc motorcycle engine on a go cart. it was pretty badass. had to reinforce the frame because of the extra weight. weilded a shift rod along side the cart . i have no idea how fast it would actually go. at around 60 mph it started to shudder pretty bad so i had to back off. i reduced the size of the sproket on the back wheel so it had a pretty wild hole shot. had to create small wheelie bars on the back and weight the front just to keep the wheels on the ground. spent a lot of money replacing tires. this thing would burn a set of tires up in a flash.