WELL, it is a pain in the ass process... Being that you only receive a bill of sale.. If you get the seller to give you as much information on the bike- specifically the chain of ownership. To that -if you have any friends in local law to run a trace on the origanal owner.. Best if you could get that person to help, file a lost title with DMV..
If you find out that the bike has a salvage title, Find out who, or what agency filed it salvage.. DMV should have a form - for that agency to fill out so that you can take it back to DMV..
Then you get the process of making the bike DMV worthy for the road..
Reguardless- You will back at DMV to fill out forms - For either title work, or BONDing a title with DMV..