im quite sure that here in NY, all private party vehicals sales are "as-is" .... EVEN IF ITS NOT ON THE BILL OF SALE!
i could write out a receipt that says: 1973 XXX, bought for $1000 and paid in full and state law already dictates that that bill of sale is "as is"
the only time the new buyer can do anything is if he has some sort of promise otherwise ... either on paper, on tape, or can bring enough witnesses to court to convince a judge otherwise
sold equals sold .... no "indian giver" type ***** allowed