Re: Motorized Pedicab?
The 4 stroke kits available don't get bigger than about 49.4 ccs (Honda GXH50). If you are good mechanically, you can make any size engine work.
However, I would not think that top speed is first and foremost with that bike, so that honda or a clone may work fine provided you gear it down far enough. Would you really want more that 20 mph? I think you could get a 50 cc 4 stroke to get close to that geared down.
BTW- I mention only 4 strokes because you referred to 2 4 stroke engines.