Hi Clive
Judging from the list of bikes you have, I am sorry if if some of this is a bit too basic, it is always difficult to know how good folks are with the greasy aspects of ownership.
Bends and bows in the fork legs can be found by rolling the bare legs on a flat surface.
Drain off the oil and see how well each leg moves by itself. If you find a tight spot its worth dismantling the forks completely, washing out the sliders and making sure the lower bushes slide freely.
When reassembling the forks, oil the bushes and lubricate the oil seal lips and exposed leg with a smear of grease so that the seal does not run dry. Each leg should move in and out smoothly, easier to check if they are drained off.
Any pitting in the fork leg will compromise the effectiveness and longevity of the seal....short term fix is epoxy filler to fill the pitting and smoothed off to match the fork leg. They can be ground and hard chromed back to size, but the cost may be prohibitive compared to a new pattern leg.
With the mudguard bridge unbolted or removed, reassemble all loosely and then tighten as directed in the manuals....start with the top nuts, pump the forks to settle them, align the front wheel, pump again, tighten lower yoke pinchbolts, pump again, then wheel spindle, finally top yoke pinchbolt. You should now have forks that compress and rebound. If they bind with the mudguard bridge reassembled, that's an easy fix. If set up correctly and the return is poor but with no evidence of binding, and filled to spec. with the correct oil, the cause is weak springs or blocked oil bleed holes as mentioned above. The mudguard bridge is important for the stability of the sliders, but must not apply any sideways force to them, otherwise the bushes will bind.
Swarfy