I built a scooter a few years ago and was told that it would be next to impossible to certify it. The best advice I got was to use the front end off a moped or motorcycle with the serial number on it, then register it as that bike, and it would be considered modified. That's easy enough, just hack the front end off a junk moped and weld it on in place of the bike front end it had, actually that was held on by u-bolts cause i don't have a welder. The hard part is finding a mechanic who's dumb enough to certify it. I wish I could get that thing certified someday. It's fun to drive, looks like nothing else you've ever seen and performance wise beats the crap out of my moped.