How can you make a motorbike out of a 3.5 hp push lawn mower?

i took a couple of wheel barrow wheels, welded a frame using the front of a bmx bike for the steering. build the engine in. find a riding mower transmission. couple the tranny to the mower motor by a belt and pulleys. leave the belt loose and put a third, freewheeling, pulley to tighten the belt (this will act like a clutch) gear the tranny out put to the rear wheel. my 4.5 horse Murray ran through a 3 speed rider transmission will climb a 30 degree slope in first and easily does 3omph in 3rd which is scary fast. half the fun is figuring out how to build it, have fun