Just to throw in a 'some thing different' I used to race a lawn mower!! I couldn't find a Youtube that you could clearly pick me in but this will give you an idea. Vic Mowers run motor bike engines and the "A" Mod's are 450cc and you could imagine how one of these would go with a YZF or CRF 450 engine Mine has an old CB 400 four in it, I can't keep up to these guys now http://youtu.be/b9pjZf5z_ek