If you can find the previous owner, then get a bill of sale. If you can't, but you can verify it is not listed as stolen, then get a buddy to write you a bill of sale, and be done with it. The DMV may require you to get it inspected by a sheriff, but that will be the end of it. I had one inspected that was out of the system since 1976 (who knows if it was stolen, legit, if any owner ever registered it since 1976, etc). I had to wait two months until my appointment came up, walked out to the bike with the sheriff, stood there for ten seconds while he inspected it, then walked back in to get my paperwork.
Camelman