If your stock seat foam is way too hard (the DRZ, for example) you can modify the foam to improve it's comfort. In this tech tip, we'll remove some foam so the seat foam can compress a bit more. The holes are drilled from the bottom of the seat foam so they don't collect water.
Tools required are pretty simple, but with one "trick" tool, a home-made hole saw. I haven't tried a store-bought hole saw because they're very thick and coarse, and might rip the foam rather than cutting it. Here is the hole saw that I made. It's 5/8" brass tubing with notches cut with a triangular file:
Start by removing the seat from the bike, then the staples from the seat cover. I normally lift the staples with a straight screwdriver, then pull them all the way out with needle-nose pliers. Be careful with the screwdriver, you don't want to poke holes in your seat cover.
Now remove the seat cover. Remember the orientation and tailoring of the seat cover so you can reinstall it correctly. It may not be a bad idea to put alignment marks on them.
Remove the seat foam from the seat pan.
Lay out a grid of lines about 1.5" apart. The grid should be over the thick part of the seat.
Push the hole saw slightly into the foam, then start the drill. This will make a neat hole. Trying to push a turning saw into the foam doesn't work very well.
Here's the finished grid.
The stock seat foam was glued to the seat pan, so I glued it again. Just a bit at the front and back. I figure it will help the seat keep it's shape. I used weather-stripping adhesive, A.K.A. "Gorilla Snot".
Re-install the seat cover. Pull the cover on, and start at each end, pulling it snug, but not drum-tight, then hit it with a couple staples. Next do the middle of each side, then fill in the edges. Check frequently for wrinkles.
Word of caution, if you're buying a stapler for this job, spend the money for a good one -- this particular model won't drive the staples all the way into the seat pan, and I have to beat them in the rest of the way with a hammer.
If you have any additional questions about seat covering, this tech tip will help:
I've found that this mod gives very nice initial softness & comfort, but once the holes collapse, it's still firm enough to keep you off the seat pan, which is an improvement over plain soft foam.
Now go for a good long ride!