Installing a ZX600 shock
The ZX600 shock is a definite upgrade for your rear suspension. Most think it's better than the EX500 shock.
The first thing you'll need to do is take off all that bracketry surrounding the air valve. Then check to see if it holds pressure and change the oil before beginning the install. Most owners find they need little or no air in this shock, so that may not matter, but you should indubitably do an oil change.
1. Put your bike on the centerstand. Take off the seat and remove the left side panel with a phillips screwdriver. Set the plastic away from your work area to avoid damage to it.
2. Optional: Remove the coolant reservoir using a 10mm socket on the two bolts. Zip-tie the reservoir out of the way (the frame towards the front works). Here's what you're looking at now...
3. With a 17mm socket, begin removing the upper shock mounting bolt. It threads into the frame, so there isn't a nut on the other side.
4. Now, remove the lower shock mounting bolt. The bolt head is 17mm, but you'll need another socket/wrench to stop the nut from spinning with the bolt (nut = 19mm). An impact wrench (if you have one) will work wonders for this step.
5. The shock will now drop out (with a little persuasion). Put the nut back on the bolt and set it aside. Now you will need to remove the bolt to the left of the lower shock mount. Again, use the impact wrench, or a breaker bar, and set aside. This will aid in the positioning of the larger ZX600 shock.
With both shocks out you can compare the two. The ZX is much wider and heavier, but slightly shorter.
6. Now you need to slide the ZX shock into position. This can be tricky. There is only one way the shock will sit correctly - the adjusting screw up top should be on the right - closer to the rear brake pedal. If it is reversed, the screw will hit the frame and the shock will not align. Be careful not to harm the air line/connections. Insert the bolt (remember, there's no nut) and tighten it down.
7. Before attaching the lower shock mounting bolt, assemble the arms.
8. To mount the bottom end of the shock, first you need some 1/2" washers to act as spacers for the bolt. Without these, the shock will have too much side-to-side play. You may also find that the lower mounting bolt from the stock shock is too short. You can replace it with one from the ZX600 shock, part # 92002-1464 (BOLT,12X60). It is 5mm longer (available from the usual OEM suppliers).
For the assembly to line up, you need to raise the rear wheel because the new shock is shorter than the old. A piece of 3/4" plywood and a 2x4 will help lift it. Once you work the bolt through, tighten down the nut.
9. Now, about that air hose: It can be zip-tied along the top of the swingarm, or anywhere else that the valve can be accessed. You will want and need to check pressure and adjust as necessary. View from below:
The view from above:
10. Now, double check the upper mount, lower mount, and rod assembly bolts, throw the coolant reservoir back on, reattach the side panel, pop on the seat, and you have a MUCH better rear suspension than stock.
Checking the pressure in the shock
There are two ways to do this. Whatever you do, don't use an air compressor. The air reservoir can burst if you put too much pressure in it, and then you get to start all over again.
1. Get a shock pump, or other low-volume pump, from a bicycle store. Make sure your bicycle pump is accurate at pressures as low as 5 or 10 psi. This may be difficult to find. The pump has to be low-volume; filling the reservoir slowly is important. This kind of pump may have to be combined with a pressure gauge that measures in 1 psi increments (see warning below) as most of them don't have gauges that read low enough for this application.
2. If you have a portable air tank, set the tank to the pressure you want to put in the shock, then let them equalize. This works whether you want to raise or lower the shock pressure. Don't trust the gauge on the tank; use your precision tire gauge on the tank's Schrader fill-valve.
If you put a tire gauge on the air hose, some of the shock oil may leak out. Try putting the bike on its centerstand and adding a pump of air before checking pressure, to force any potential oil back into the shock and minimize leakage. If this happens too many times, plan on either topping it off or changing the oil again.
Max psi is 28, so be careful. It doesn't take much to get that high. Pressure settings are a matter of personal preference. One rider with an "A" series ('85-'87) uses about 15-20 psi. A different member with an "A" series says he uses about 5 psi around town and increases it to 20 for sporting weekend rides. One person with a newer "C" series ('88-'97) shock said that he usually found the shock to be stiff enough without any air in it. All of these guys weigh in the 140-150 lb. range. You'll have to test for yourself and see what works for you. Be careful when adding air, though.
What you're looking for
You want a shock from a ZX600 A, B, or C (1985-1997). You don't want one from a ZX-6 (ZX600E) or a ZX-6R (ZX600F).
If it looks like this:
Or like this:
It won't fit.
It has to look like Fat Boy here: