1) Don't loose that bill of sale (make coppies) Otherwise they could say you stole it.
2) Don't leave the bike out where someone can run off with it.


If you got it in writing that he'll pay it off, your in a better position. Otherwise you may (even after some trouble) get a bike that you still have to pay for or end up getting it reposessed. I hope they have they been making the payments at least?

I feel for you. I've delt with a couple flakes and it's hard to tell what it will take to get them to do the right thing. Might just have to cut your losses the best you can and let God deal with'em however he sees fit.