How do I remove the fork caps/pistons?
Nomenclature note: Fork caps and fork pistons are the same thing, and you will see the terms used interchangeably.
Jack up the front of the bike so you don't have to worry about the front forks collapsing while you're taking the springs out.
Remove the handlebars by unscrewing the four hex-head bolts on top of the upper fork holder.
The fork springs are held inside the forks by a piston (that thing with a dimple in the top) which is secured by a snap ring. Use one of the methods at the bottom of the page to push the piston down, so you can pop the snap ring out with a pair of needle-nose pliers. The fork caps will only slide down about 1/4 inch. That is all you need to get the circlip out. They won't go down much, if any, further.
This whole process is much easier to do while the forks are on the bike, as you need to hold the upper tube and compress the spring in order to remove the clip.
Once the snap ring is out you can let up pressure on the cap, but not too fast! The piston will rise very slowly because it's in there tight, but once it reaches the top it will want to shoot out like a champagne cork. Just in case, don't put your face over the fork tube while doing this. Just slowly ease the piston out.
Underneath the piston are some miscellaneous hardware like a large washer and a spacer. The spring should be visible once the hardware is out. Replace it and assemble in reverse order. See here for replacing the fork oil.
Tools for removing the snap-ring
Some people recommend buying a gear puller for this job. Gear pullers are expensive...
...you can use a simple two-jaw puller (~$5) for this job.
Sink tap pullers will also work.
You could also probably find a battery terminal puller or a windshield wiper puller that will work as well.
The fork tubes need to be held in order to press down the cap. The easiest way is to bolt them into the triple clamp. Then, hook the gear puller onto the triple tree and clamp it down so that the fork cap moves down about 1/4 inch.
Remove the clip by first using a small screwdriver to pop out one end. Pry under the end next to the gap in the ring. If you have trouble, try pushing the snap clip/ring downward.
Then, grab it with a pair of needle-nosed pliers and pull it out.
One big phillips screwdriver is very enough for this job. Using a screwdriver is faster than a gear puller.
With the fork resting on the ground, push down on the cap with the end of your socket wrench, and use a dentist's pick to remove the clip. Once you look at it, there isn't any question as to how it should be done, and the whole gear puller thing seems like WAY too much work for such a simple task.
Partially screw a screw into an exposed stud in your garage or shop, pointing downward at a 45 degree angle. Hold the dimple of the cap against the screw and push upward on the fork, depressing the cap. With your dominant hand, pop out the circlip with a screwdriver to get it started, then pull it the rest of the way with needle-nosed pliers. Similar thing to put them back in.
The important thing to remember about that snap ring is: Go to the hardware store and replace that damn thing with a proper circlip (the kind with the holes in each end). It uses a specific tool (circlip pliers) designed for removing those kinds of clips ~ It makes for much less work.
The snap ring/circlip to use is 1 1/4" (N1300) or 32 mm (DIN 472) Internal Retaining Ring. They can be found, in plain (coated?) steel, at Home Depot in a pinch. You may want to use a stainless steel one instead.