http://www.treasuretrovetoys.com.au/prod8.htm check out that sight They say the engines have a practical rpm from 4500 - 32 000 it could be a exageration or I could be wrong but I will do some math to see If that rpm makes sense with our gearing and tire swell. But it is funny their add says it could make your 2 speed buggy hit 70km/h that is exactly what I figure mine will go.