I registered my bike as a moped in Michigan.

I just went up to the secretary of state with the bike's serial number (1950s Columbia) and told them it was a "Whizzer" I was restoring. The lady had no idea what I was talking about, but asked if I had the title. I said I didn't think it was ever titled and that I bought it at a garage sale.

She put it in for a title check (they run the SN), and called me to come back when it went through. Since it didn't show up as being previously registered they issued me a new registration and gave me a license decal.

I know some think it sacrilege, but legally my bike is considered a 'moped' now, has a license sticker on the fender and I have a registration in my wallet. I have ridden past several police officers and they haven't given me a second glance.

Here in Michigan they don't inspect the bike or anything.