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Front Forks

The front forks are damping-rod forks. In the simplest term, oil is forced through fixed orifices. Fixed-orifice forks have very little "low-speed" damping and a lot of "high-speed" damping (vertical wheel speed). With very little low-speed damping, the fork dives excessively, and with a lot of high-speed damping you'll get a harsh spike.

T.R.A.C (Torque Reactive Anti-Dive Control)

To reduce the affect of fork dive, Honda developed the "TRAC" system. One of the two front brake calipers is hinged behind the fork leg on a pivoting link. When you apply the brakes, the pads grip the disc and this tries to drag the brake caliper around with it. The caliper pivots, pressing against the anti-dive mechanism's activating valve and closing off the fork's compression-damping oil passage.

This valve, in the shape of a piston, is normally held open by a spring. Forward weight transfer during braking compresses the fork, raising fork oil pressure against the underside of the TRAC activating valve and, through the valve, pushing against the caliper's braking torque. These two opposing forces - fork-oil pressure and braking torque - interact through the valve to provide progressive anti-dive. Hitting a bump causes a sharp pressure rise in the fork. This rise can cause the valve to push hard enough against the opposing force of the caliper to open, partially or fully, the normal compression-damping passageway. This opening allows the fork to respond to a bump. Moreover, TRAC's design provides a constant modulation between fork anti-dive and bump response.

The TRAC system has a four position adjustment on one of the fork legs. The adjuster controls a small secondary oilway parallel to the main compression damping passageway. This secondary passage provides a way to bleed-off fork-oil pressure from under the anti-dive valve. The rates at which this bleed-off occurs are controlled by orifices, the size of which can be controlled by an external adjuster.

Position one corresponds to the largest orifice, which offers the least resistance to the passage of fork compression-damping oil; positions two and three expose progressively smaller, more restrictive orifices, increasing fork damping pressure. The fourth position exposes no hole; all fork-oil pressure comes to bear on the valve's underside and against the braking torque.

Normally, a fork has much lighter compression damping (one-fourth) than rebound damping. In the TRAC system, when the anti-dive seals off the main compression-damping passageway, compression damping becomes two or three times stiffer than normal when the adjuster is set on position one. On successive settings the compression-to-rebound damping ratios become increasingly biased toward compression.


The part of the fork that is clamped to the triple clamps is called the "tube" or "upper". The part of the fork that the axle goes through is called the "slider" or "lower". Inside the fork from top down:

(To prevent the fork oil from leaking out at the junction between the lower and upper, an oil seal is used. The oil seal is held in place by a circlip. Above the oil seal is a dust cover)

Fork Oil

The manual recommends using ATF fluid as fork oil. As ATF fluid viscosity is not rated and may vary from mfr. to mfr. and bottle to bottle, Fork Fluid is recommended. Fork fluid comes in 10w, 15W and 20w viscosity. Normal recommendation is to use 10w unless you are toward the heavy end of the scale or ride 2-up quite often.

Replacing oil seals

To replace the oil seals all the oil must be drained out of the forks. Some models have a specific drain screw while others may drain from the damper bolt.

Grind off chamfer seen here on top edge of socket




- You can try to refresh the seals by using Pete Springers method. It doesn't take much time or money and is well worth the effort. SpringerForksSeals.jpg '

Another method that works to remove gunk from the seal

  1. Clean the fork upper just above seal.
  2. Wrap a couple layers of QUALITY packing tape (like 3M) -sticky side in - around the fork just above the seals. Try not to have any wrinkles. And cut the tape cleanly, you don't want any pieces of tape ripping off and getting stuck in the seal.
  3. Then lock the front brakes and forcefully rock the bike back and forth pushing the tape into and out of the seals.
  4. Remove the tape (you can CAREFULLY cut with a razor blade if you have to - don't mar the fork surface) and clean the fork upper and lower of any oil.
  5. Go for a ride and see if any oil/dark ring shows up on the fork upper. A slight film you can only see on your finger when you wipe it on the fork upper should be OK. Any more and you will need to replace the seals.