Send him a letter some way or ways that you can prove delivery (e.g. by Fed Ex with tracking; by simutaneous regular mail (to see if it's returned as undeliverable) and certified mail, return receipt requested; etc.) which states that 1) you had allowed him to store it as a favor--i.e. makes clear he was not paying you rent or storage charges, and otherwise were under no obligation to keep it; 2) that you are no longer willing to keep it; 3) when you first told him to pick it up, and the number of occasions and how you have previously asked him to take it back; and 4) that you are giving him 90 days to remove it or else you will consider it abandoned and dispose of it however you wish. Repeat this at 60 days, giving him a 60-day warning; at 30 days, giving him a 30-day warning; then again at 10 days. Make sure you keep proof of all your contacts; then if he still doesn't take it make or schedule a mutually agreeable time to get it, do with it as you will.