Thanks everyone, I can fix most things. They are 2001 Z1 bought about three years ago on here. I pulled them apart and replaced the seals with some from RWC no probs.
They've been used a lot since then and have developed two faults:
1] No rebound adjustment anymore.
2] Play between the stancions and the lowers making it feel like I have a loose headset when I ride.
I've downloaded the manual and providing I can get the spares and don't need special tools I'll give it a go [nothing to loose].
2) is the bushings are done. Finding replacements might be tricky to say the least. I think at some stage everything has to become parts to keep the rest going.
Possibly the only way youll find bushings is to strip an old fork and hope theyre not AS worn.
Z1's have 2 rebound cartridges :? Im guessing its clogged up with grease or sediment or some such thing so a service to remove them then clean out with degreaser(cup of it, place cartridge into cup and pump ) Theres a wee hole, might find a sewing pin will clear out if thats blocked.
I would strongly recommend using a torque wrench when reassembling.
The only thing I would add, is to do with the issue with rebound - you dont say whether the problem is that current rebound is too quick or too slow. If the problem is to do with rebound being too slow, then what dyna has already been said will help (especially after three years using the same oil with heavy use). However, if the problem is that rebound is too quick/harsh, then it could be that a seal/o-ring within the hydraulic cartridge has gone, and therefore the cartridge cannot draw oil in at a measured rate when extending. That's a trickier problem, as I'm not sure how available replacement seals etc are.
I would also underline the advice over torque wrenching...I've found out the hard way that over torquing (not by me I hasten to add), can end up with fairly catastrophic results!