If the seller can't tell you anything about it, I'd say that a good price would be:
(new price / 2) - cost of a full service.
So maybe $200? If you buy it, send it off to a good shop and tell them what you want to use it for, they can check it out, test the spring, fix any seals, recharge the gas, and change the spring and valving if necessary.
If it was sprung for a 180 pounder for track use, it might be OK for a 220 pounder on the street. But if you change the spring rate you certainly need to change the valving. Best bet is to lowball the seller and if he goes for it, leave the sorting out stuff to the pros.
(new price / 2) - cost of a full service.
So maybe $200? If you buy it, send it off to a good shop and tell them what you want to use it for, they can check it out, test the spring, fix any seals, recharge the gas, and change the spring and valving if necessary.
If it was sprung for a 180 pounder for track use, it might be OK for a 220 pounder on the street. But if you change the spring rate you certainly need to change the valving. Best bet is to lowball the seller and if he goes for it, leave the sorting out stuff to the pros.