If you ride one outside of your own state, I can guarantee that at least one state will require it to be registered and licensed if driven on any public street and may require all riders to wear a helmet. At the very least, you'll be pulled over every time a P.O. sees you, get a ticket and possibly be made to park it.
Besides that, riding one outside of a residential subdivision at that speed will give you an excellent chance of becoming somebody's hood ornament. Better to register, license and wear a helmet and not need it, than the other way around.