That's the one on my bike meant to be 4 hp and hit 12000 rev .it fits a 4 stroke mount.and gear box . only problem I found is that it's loud very loud and any muffler that restrict air will make a big difference in power . with a 20inc wheel and a 52t sprocket my One hit 67kmh all day everyday never changes. And I don't need to pedal ever .I had a 54t on it and it would pop wheelie just like a little dirt bike once the power kicked in it will rip a 66cc in half maybe not on top speed but getting there its 3 Times faster my dad on a 49cc for stroke flat out doing like 55kmh I passed him like he wasn't even there lol...The motor its self is so clean ports are big full cranck comes with a hp carby Reeds hp head its all done already form the box ..if someone made one for a bike that isn't to loud you would never need another engine .Just the pull start once a year. Its so nice in Side the finish it's better then my cars internals .
