How much would you knock off the value of second hand forks for damage? Specifically, chips to the stanchions (3, small) and air getting past a top-cap O-ring?

It they're damaged then you'll have a smaller pool of buyers so it's more up to them than generic advice.

"How much is the repair?" is the cardinal question.

Phhhhhhhhhh. It depends. What fork? What is it worth undamaged? How old? Can you repair it or will you have to send it off?

air getting past a top-cap O-ring?
This REALLY depends on what fork it is!

mail me the details and I can give you a rough idea of possible costs if you like.

Open bath bombers, 2007, worth £90-100 in good nick. The leaky seal is the ETA top-cap O-ring, that gets squashed down against the uppers to seal as the cartridge is tightened up.

I think it's potentially DIYable, but it looks like a fair bit of time to strip, clean, fill the marks and reassemble.

Offer them £50, tops.

There's loads of used forks around at that price so unless you get a bargain it's just not worth it.

RS Recons go for about that price….

Cheers PP, that was pretty much my thinking.

LoCo, I've emailed you.

I have some scuffed up, ever-so-slightly less plush than new but still recently serviced Pace RC41s in my garage…

tron ygm.

Wait and buy something else.

Molgrips how much?

LoCo, I've emailed you.

As good as LoCo is, if you spend £50 on the damaged forks, I'll bet you'll still spend more than the fork is worth.

If it was a £300 fork, and you could get it cheap and fix it, then it might be worth it.

Look elsewhere IMO.

Er, not sure how much.. maybe £120 posted? Like I say they work perfectly well, they had just lost a touch of plushness for some reason.. I only changed them because the rear sus was still buttery smooth and I started noticing it. On an HT I doubt I would have changed them. Oh and they are the kind with good seals – no water ingress in 3 years.