Im in illinios and you need to check your citys ordinences then the state law....... im in evanston IL and there is no Pedacycle law so it goes to state law....
motor assisted pedicycles, according to the IL DMV, are legal without insurance or a licence plate if it is under 50 cc and does not reach 30 mph in a mile or so of acceleration.............. must have a light and a reflector .
2 break hp or less
check out 625 ilcs 5/1-148.2
they do require bicycle registration..... i would get it registered before the motor is on it.