You state the bike is in your name? Does that mean the title and registration shows you as owner or is his name on the title and registration? If your name is on the title with no lienholder, it's yours to do with as you please. If there's a lienholder it's theirs and if he stops paying, they can repo the bike. Check with DMV to ascertain who has title if you can't and make sure he never borrowed against the title before you two went your ways.
