I think the cops would have to know a bit about bikes to see some thing that was not obvious. 49 cc and 750 are the magic #'s with licensing and insurance. If you crammed a bored out cr80 motor into a scooter, most cops would not have a clue. If you jammed a bigger than 750 motor into a smaller chassis, it would most likely go nu-noticed. If you ever got in a wreck with either, and were under insured or licensed, then the trouble would start.
WTF, Over?