Yeah, I am building a motorcycle, but note that I stated lightweight, and again, I saw this thing on a God damn kart with tubing HALF the size and thickness of a bicycle frame! I'm going a (slightly) safer route in choosing a mini chopper frame.
What I want is a bike barely anyone has dared build. The main application to this predator is power washers, lawn mowers, go karts, mini bikes, that sorta thing. I'm not a stupid dickbag who will try to go from zero to sixty in point five seconds. I know this engine is three times larger than a 212, and I also know that when experienced guys warn me against going with something so large, you are probably right and there are likely huge safety problems.
But im doing it anyways, and it's not out of idiocy. A 20hp engine is definitely not something to mess around with, as one mistake can be fatal. But I see it as a challenge, from every one of you who say I should just get a motorcycle, to build this safely and amaze you all. I'm planning on this engine being able to go at least 140 tops with a jackshaft. I might just replace the existing shaft with a longer one and support it from the seat tube to lower mounting costs. Oh, and all materials will be 2ga steel at the least (besides the frame).
P.S: I didn't mean to jack your thread necromancer. Have you been able to make any more progress?
, the chain, the jackshaft (this is the reason for the disclaimer below), and finally, the throttle handle, shifters, grips, a comfortable seat, and a good ice cold bottle of virgils root beer sitting on the side of the tank. BTW, I also have an aosom cargo trailer rated to 180 pounds, so if anyone could give me any pointers as to how I could turn it into a soundbox with a cooler, it'd be much appreciated. 
