I sorta knew that this was going to happen since a moped is rather hard to define. What does your moped become when you overbore or big bore it or when you add a kickstart? Its all of a sudden a motorcycle now? I'll try to find it to cite it but in one of the old moped books from my library a moped was defined as a "motorized two wheeled vehicle possessing an engine displacement up to and including 125cc and pedals".
and what about the moped racing over in europe? If you've ever seen some of those videos, there's no way that they're running 50cc machines.