California considers anything with less then 4 wheels to be a motorcycle. Although I have been riding for years, have a motorcycle endorsement, and wear a helmet while using the Morgan, I understand California does not require either for 3 wheel vehicles.
When Arnold was the Gov, he talked his way out of a ticket at the Rock Store by stating that since he was on a Harley with a side car, he didn't need a helmet or endorsement. They let him go....
Roland