I think now that I look at it-I'm gonna use the 5.5 on a go kart. This little bike went so nicely with a 79cc Greyhound.....Maybe I'll go get a pee-wee Predator. The 79cc engine doesn't have the shaft size issues with the clutch that are present on the 99cc. I have a 99cc on my Grand Prix,and it took a lot of machining to get the clutch to fit. But I love the way it runs.....I put an AGK carb on it with a bigger venturi,and an open exhaust,and it really flies in the upper rpm ranges. It sounds like an old Yamaha SR500 single,too.