The Missouri Department of Register states that a motorized bicycle does not have to be registered as long as it has:
- An automatic transmission
- 2 to 3 wheels
- A motor no bigger that 50cc (and under 3hp)
- A top speed of no more than 30mph of flat ground
You must have a valid drivers license to ride a motorized bicycle on public road in Missouri. You do not need a motorcycle license.
You do not have to register your motorized bicycle in Missouri according to the law, as long as the bicycle fits the definition as outline above.
If your motorized bicycle exceeds the limits above then you must register it as a motorcycle.