Have one of those myself. Pretty durable little engines. 98cc, and they are 3 hp but at 4400 rpm. Also have an old bike sitting around that has a retro look to it. I've been thinking about putting them together too. Engine is fairly compact, but in my case I will have to shorten the crankshaft to fit between the pedals. I'm thinking direct belt drive on mine with about a 14 inch driven pulley, it came out to about 35 or so mph at max rpm. Just need some ambition.
Keep us apprised of your progress.
Denny