A mini motor bike for children is powered by 4 hp single cylinder gasoline engine governed to run at a maximum of 1850 rpm. a 6 inch centrifugal sheave which acts as the clutch, is mounted on the engine output shaft rotating at 350-1850 rpm. Design a v-belt/chain drive which limits the top speed to approximately 17.5 mph given the outside diameter of the drive wheel is 16 inches. The driven sheave and the drive sprocket are mounted on the opposite ends of a free turning jack shaft.