I live in california. 1 week ago today I sold a used motor that last I knew ran fine. I signed a bill of sale saying guarenteed it ran because from what I knew it did. Now a week later the people are calling saying they got it installed [in a 1996 honda civic] which my ad states its for a 92-95 honda civic, now saying it works but there is a knocking noise (which I truly was unaware it had) and they want there money back. I say fine cause I'm not a mean person. But then the guy says well it will be a few weeks because he has to get together the money to pay his mechanic to take the motor back out. Am I obligated to refund him almost a month later when he will have the motor this long in his care?