after removing the intake restrictor, and doing intake porting. biggest front sprocket that fit. 50cc's got me 45mph downhill. much happier with my current air cooled antique 360cc 4t beater. but at 15 a 45mph puch maxi was a game changer. If I only had game at 15. I did have metal shop at 15. milled the shit out of the head. needed 93 octane. was an amazing hill climber. I also bought the smallest front sprocket.