View
Point: |
| Subject: Suspension Part 2 Why is it that the majority of riders are focused on keeping the oil fresh in their rear shocks? When was the last time your forks were serviced? At ten hours, 20 hours? Some time this year? Did you know today's forks are full of delicate bits and pieces that require more frequent servicing? KYB, Showa, Olhin and White Power forks all have plain bearings in the forks that are known to service techs as "engagement bushings and slider bushings," while other suspension companies call these very same parts "fork inner bushings and fork outer bushings." Your owner's manual/parts list will have manufacturer's descriptions, which will most likely be different than the suspension wizard's description. But they all do the same job! These components are very important to supply millisecond action and reaction of your forks as they travel over the quickly changing terrain. We all know the front forks are installed on an angle. This angle is the heart and soul of how the motorcycle steers. In other words it's "manners." A good example: At the end of a long straight away does it have "head shake" so bad that NASA is looking for it to launch the shuttle, or do you need a 10 acre field to turn the thing around. This "fork angle" makes the "ride sag" difficult to set up, and if you don't know what to look for, your preload will continually change every time you set the bike on the ground. Worn out bushings and old fork seals will bind and make it impossible to set up your low speed valving. Just because your fork seals are not leaking does not mean they are not tired and ready to be changed. Your fork fluid uses a chemical known as seal swell. Your seals may not be leaking, but they could be stopping the forks from performing by being too tight, creating a sticktion (a new word for friction in the suspension world). They will soon to be leaking from the overly tight condition from age and the seal swell. A simple way test for low speed sticktion is to put your motorcycle on the ground. Using a sharpie marker, place a mark just off the seal on the fork tube (Make it big enough, so it is easy to see). Next, pull in the front brake lever. While holding the front brake on, use the palm of your left hand and push downward on the cross bar pad, compressing the front forks 1 to 2 inches. Pay particular attention to where the fork tube enters the seal. Does the tube return to the original starting point? Does the fork tube have a clean and free supple movement? Ha, it doesn't ….Do not panic! Put your motorcycle back on the stand. Make sure your front axle pinch bolt is not shoved inward toward the front wheel, forcing interference between the fork tube and outer fork leg. Loosen the axle pinch bolts. Spin the front wheel rapidly. Lock up the front brake. Repeat this two or three times, but on the final lock up continue to hold pressure on the brake lever. While holding the front brake lever on reach down and torque to spec the axle pinch bolts. Once you have aligned the left fork leg to the axle, do the "palm test" over again. If you find that the sticktion is still present in the low speed part of the travel you will need to check your lower triple clamp pinch bolts; they could be over tightened (only if you have upside down forks). If your lower triple clamp pinch bolts are over-tightened, this will cause interference/ sticktion on the entire fork tube. If, after double-checking these critical areas, you find you still have stiff and sticking forks, contact your favorite suspension wizard for a rebuild. With all new bushings, seals and oil, your system should have a clean and supple movement. With the proper spring rate, you will find your race sag to be at about 75mm. The Free sag will be about 13mm to 25mm. I use the word about because the angle of the forks plays heavy on static movement. Your forks should work smoothly, reacting to the different changes in the terrain. It is normal to experience light bottoming on very large high speed objects. Remember the spring holds the rider and motorcycle up, while the bottoming is controlled by the internal valving. Your clickers only control low speed damping. If you are experiencing an ill-handling motorcycle, seek the help of an experienced suspension technician. Review Part 1 |