Yamaha's class-leading YFM50 is driven by a smooth and reliable 49cc four-stroke engine featuring an easy-to-use fully automatic transmission, making this mini ATV the best way for junior riders to start out. A simple tether system allows the adult in charge to stop the engine - and the electric-start YFM50 is the only 50cc ATV equipped with a low-maintenance shaft drive system - which is more good news for busy parents.