I bought a tokina 28-85 fd lens off of fleabay, very clean. The problem is there isn't enough focus damper. No resistance at all, and I hate it. Is there anyone who has tinkered with this lens?
If you feel you are competent enough then the lens barrel can be partially dismantled and the helicoid focusing grooves can be lubricated with a dedicated type of grease which will stiffen the focusing action. Be aware if you decide to do this many focusing systems have multi start threads so make a note where the lens finally comes apart or you will find the original focusing points are way out of kilter.
Otherwise a good repair shop should be able to to it for you at a minimal cost.
And yes, too low or too strong damping is a common issue.
I once was offered three identical zoom lenses, all for the same price, and I took the one with a scratch in the front lens, as it got the just right low damping for my use. I rather coped with that scratch than to regrease the barrel.
Well it turns out when I put in on a camera, the focus was way off. Once I got it open the threads were very dry. I put some superlube grease on there and it feels great now.