I've been reading this forum for almost a week as a guest and finally registered. This all started because I was on CraigsList and someone wanted a bicycle engine, and so I got to researching. I live in PA, and the laws here are crazy. I was thinking of a project of getting a Stingray chopper, specifically: http://www.genesbmx.com/schwinn/S6_SPOILER-_3SPD_BLU.jpg. I know for PA, it will need lights, horn, etc. I'm also restricted to a 49-50cc engine max. For the cost and regulations/laws, I know this will be really advanced, but I wonder if it would be possible to do a 100-200cc with a 3-6 speed transmission, and just "motorcycle" the bike (remove pedals/pedal chain). I've seen posts on a horizontal 50cc 4-stroke Chinese Honda clone, with 4-speed transmission, wasn't sure if there was something in the 100-150 range for this, or even a 150-200cc twin. And of course, there is the obvious of would the frame of the bicycle support the engine/speeds (i.e. would the welds be shaken apart). And living in PA, not sure if they would classify it as a scooter/motorcycle. I do know that over 50cc requires a motorcycle license (I do have a permit and a 1982 Honda CM450).