About 12 years ago, I decided to build a powered bicycle, so I dismantled my seldom used weed whacker and built a three speed drive system that attached to the motor. I put it on the front wheel of a bike, with a hand shifter so I could move it through the gears. It worked pretty well as far as pushing the bike, with top speed being faster than I felt comfortable going. I could not stand the noise and fumes, so I removed it.
I just ran into the motor/drive when looking for something else, so I figured I would snap a few photos in case someone else wants to play with a similar concept.