When I sold my Z1 SL, I gave the buyer all sorts of useful information. I thought I posted it, but might never have gotten around to it. Here's everything, for good or ill. Obviously, there's going to be some stuff that doesn't apply, as this was written as a directive to the buyer. Enjoy - S
When your fork arrives, it will have 18 psi (+) and 85 psi (-). The negative number is very apporixmate; due to the small size of the chamber, it’s tough to get an accurate reading with most shock pumps. The 85 psi as such is the indicated pressure; after the pump is removed, it probably drops 5-10 psi. I’ve achieved very good results with these pressures. I weigh 155 lbs, the fork served singlespeed duty on a Chameleon and was put through the paces. I never had it truly bottom at this pressure, though it could have gone unnoticed due to the bottom-out bumpers. My bumpers are a one-off, made of heavy gasket material, and prevent the stanchions from contacting the inside of the lowers and the wipers from contacting the crown. As a result, you’ll never get what appears to be full travel—the last ¼” on the stanchions will never be used.
From wiper to crown, the stanchions measure about 5-3/8”, sometimes as much as 5 ½”. Why it changes I’ve never discovered. One cause of this distance shrinking when the fork is unweighted (static sag) is the negative chamber taking on oil. Oil, being relatively non-compressible, in the negative chamber prevents full extension. The fact that the negative chamber takes on oil is inherent to the design; it is not a product of a seal flaw or any of the like. When a chamber compressed at 80 psi (ramped up significantly higher when compressed—say, 300 psi) draws an incredible vacuum, and with only oil to soak up, it soaks up oil! Again, this isn’t a real problem; simply hold a rag around a small allen wrench and deflate the negative chamber every so often and you’ll be fine. (The left fork leg only needs enough oil to stay internally lubricated, so the loss of this oil is not a problem. When I reassembled your fork, I greased the seals and wipers liberally to compensate for less oil in the left leg.) Keeping closer to Zoke’s 1x +/3x – recommendation helps slow the negative chamber’s thirst for oil. Higher positive pressures decrease linearity and increase rebound speed; higher negative pressures slow rebound and increase sag, though don’t have too much effect on the end-stroke. I’d stay as low as you can stand in both chambers; it rides much nicer.
Oil height in the right leg, however, is imperative. Oil is a good method by which to prevent bottoming, and the only method to properly damp things. (The HSCV-ECC damper is housed in the right leg, if you haven’t already figured this out!) When you do an oil change, it’s worth completely disassembling your fork. Zoke oil gets characteristically yucky and should be flushed entirely from the rebound/compression chamber. Remove the whole deal from both sides of the fork and pump the chambers repeatedly. If so desired, you can flush the HSCV chamber with thinner to really get things clean, but this doesn’t need to be done often. Your HSCV damper holds a good 75 ml or so of oil, and all this should be removed. After re-assembly, put 125 ml of oil in the right leg and just enough in the left (50 ml or so, but not much more). You’ll have some difficulty sandwiching the bumpers between the fork lower and the chamber, but take your time and use some needle-nose pliers, and you’ll get it eventually. While the left leg lower-bolt is easily tightened, the right is another story. I’ve never had any trouble getting it tight enough to seal and stay put, but it doesn’t get really snug like the left. The problem is, the body of the HSCV-ECC chamber rotates around the shaft, and it can’t be reached during reinstallation! I’ve no suggestions for how to help this along, but you’ll get the hang of it eventually.
The fork currently has a 6.25 wt oil in it made of ¾ Golden Spectro 5 wt and ¼ Rock Shox 10 wt. I’m very happy with this oil weight, but the recommended 7.5 weight is also very good, and makes the rebound adjustments slightly more apparent. The ECC locks out easier with the 6.25 weight, and rebound and compression are slightly quickened. I’d recommend experimenting if you’re interested, but don’t go up to a 10 wt. It’s painfully slow and very unpredictable. I’ve heard good things about a 5 wt, but never gone that low myself. Rebound/compression are most easily controlled, as noted above, by air pressures, though oil can have a drastic effect. The Golden Spectro does a very good job of keeping things slippery, but you may wish to add some teflon stanchion lube at some point—it’s fine at works great for one ride or so, but goes away pretty quickly with the Enduros.
When adjusting your air pressures, use the most accurate low-pressure pump you can afford. I’ve a crappy shock pump that I’ve had for years that just won’t give up, and I’m displeased with it’s performance. Be careful when/if you remove the ECC knob not to lose the small pin and spring that denote the detents. I’ve included two air adapters; one is stock, and is one piece, the other is my own creation and looks like it. The former fits right inside and unseats the valve stem independent of the shock pump’s presence. Use this only when connected FIRST to the pump, and disconnect the pump and adapter as one piece a the same time. The latter does not unseat the valve without the shock in place, and is much harder to use, but potentially more accurate. I’ve put a bead of solder on the end of a pin, and the pin end must sit right on top of the valve. Screw the shock pump onto this adapter while it’s in place, and remove the shock pump before the adapter. You’ll develop a feel for one or the other, and sometimes the valve cores get sticky and require the homemade adapter to be used.