Quick And Dirty Twin-Chamber-Fork Seal Changes - Dr. Dirt

Use your thumbnails to pry apart the first bushing. It is usually pretty easy, and when spread just a bit, it will easily slip off the end of the fork tube. The cleaned bushing should be uniformly gray on the outside. If the underlying brass is showing through at any point, look for damage inside the outer fork tube. Your quick and dirty fork seal change is over, and you'll need additional special tools.

The rest of the parts slide right off. Lay them out in the order they come off. The washer that goes between the seal and the bushing isn't too critical for this Showa, but a Kayaba has a machined part that must go in the way it comes out. The second bushing should have the uniformly gray color inside. If the brass shows through in streaks, look for significant damage in the steel inner tube's surface.

Clean the tube extremely well, then under good light, inspect it for nicks that may have cut the seal. Use a razor blade to judge any imperfections you see. If the razor catches on any small pits, they will need to be dressed and have the edges removed before the new seal is put in. Nicks will almost always be at the back of the fork tube. Deep or large scrapes or gouges may not be repaired successfully. To keep the fork light, the outer tubes are very thin, and they can be dented right through fork guards in a crash involving another machine. The inner tube must be replaced if the damage is major.

Small nicks from the front tire hucking rocks at the rear of the tube can be dressed. I use a fine-grit, tapered sanding tip like this one in a Dremel tool. A Scotch-Brite tip or a Cratex tip (grit in a rubber compound) work well, too. Don't get carried away. You just want to knock down the edges. As soon as the razor blade will slide across the nicks without catching, the nicks won't bother the seal.

Dump the oil from the outer fork leg into a drain pan. Make sure the oil drains completely. Once the outer tube has emptied, push in the cartridge rod and release it. It should spring back to full extension if the cartridge is still pressurized fully. If the cartridge rod doesn't return, the inner cartridge must be serviced, and it will require more special tools.

Since we are only dealing with the outer chamber oil, we can fill it from this end and not bother with removing the top fork cap or the cartridge. The manual will tell you the correct volume. We put in 10cc less than the specified amount since we couldn't be sure that the outer tube was completely drained.

To complete the reassembly you will need another special tool, but you can make this one out of a plastic sandwich bag. Cut off the corner of a quart-size bag.

Set the bag corner aside and use some light grease on the seal and the wiper.

Put the cut bag over the end of the steel fork tube. Without the bag, the machined edges where the fork bushing sits are very sharp, and they will cut the seal while it goes on.

Slipping the greased seal over the bag keeps the seal safe. Slide the wiper on first, drop on the snap ring, then carefully work the seal over the bag and the sharp edges. After the seal is on, remove the bag corner and slip on the spacer and bushings.

The assembled inner leg should look like this. Set it aside while you prep the outer tube.

With the fork in an appropriate vise or held upright by your helper, ease the fork spring over the cartridge rod. Slide in the damping adjuster tube. The bottom end is indexed in a Showa, but not a Kayaba. The rod will only drop in fully when it is rotated correctly. On the Showa the rod is below the top of the cartridge rod, but on a Kayaba it extends a bit above the top of the rod.