I sold a bike to a guy last Thursday and I need advice. He came to my place, rode the bike around, and asked me questions about the bike for about an hour. He expressed concerns that the bike may be too small and decided to wait before purchasing. After talking for a little longer, he decides that he wants to buy it so I wouldn't sell it to someone else. He pays me and takes the bike. He keeps the bike until this past Tuesday and contacts me saying that he wants his money back because the bike is too small. I tell him that I am reluctant to refund his money and he threatens me with a lawsuit unless I comply. So far, he still has the bike (I assume) and I still have the money.

So......what are my rights? I certainly would refund his money if the bike was not mechanically sound, but he wants a refund because he decided he needs a larger frame. I feel terrible that he feels he made a bad purchase, but should I have to pay for his mistake? Thanks.