I recently saw an air/oil fork kit and an equalizing fork kit for sale, they said they were for racing but how does this system work. It looked like tire stem valves mounted to the top of the fork. How does this help the bike?
hond used this on their bikes a lot in the 80's. It is a way of making the dampning on the fork adjustable. Basically you use air to pressuize the forks and increase the stiffness. Makes your front end adjsutable to any track condition. The equalizer is there to make sure that the pressure is equal between the forks, when I used to race MX there were still plenty of guys who had air forks without equalizers and it was not oncommon to have one fork leg stiffer than the other (not that much of a problem on dirt, but it changes the handling on road courses). Typically the setup consists of to shrader valves in the top of the fork cap and a hose running between the caps to equal out the pressure.
MY cb900F has this system and I just got another system for the cb750. Easy to install but if you are not careful you can cut the life of your fork seals pretty quickly.
Pretty simple to add. Drill and tap each fork cap (off the bike of course) for 1/8NPT and plumb between the two with removable fittings, I like push to connect. Add a shraeder to one or both caps as well and you're dialed. It only takes a pound or two to make a big difference. I recommend getting a low pressure gage ie; 0-10psi to test with.
The air pressure really doesn't have any affect on the damping. It simply provides an air spring. The problem is that the volume of air in the fork tubes is so small that a small change in static pressure has a huge change in spring rate. I gave up on it in race bikes and just either added preload spacers or changed springs. As a side note the 1983 or 84 Harley FXSRT had a system that added the volume of the crash bar to the fork air volume to a more forgiving system. It was designed by Eric Buell while he still worked for Harley. It might be interesting to try adding an air resevoir to the system and try it.