Since I've been putting my first engine kit together I see my 10 year old son is getting envious LOL. So I thought maybe I should get him one too so we can work on his together. I would install the engine on his MTB with the smaller 24" (I think) rims. Since the circumference of the 24" rim is smaller than our 26" rims his top speed would be less than our bikes. I'd get him the 50cc engine version and additionally put in some safeguards to limit his top speed. He already has one of those little 50cc kids quads that he rides at camp in the summer but of course the quad having 4 wheels I feel is a lot safer and even though he's driven that darn thing into the side of the barn a few times at a decent clip when he first got it he didn't get hurt. SO what do you guys think? Good or bad idea to get an 11y/o one of these?