Most motorcycles rely on some form of telescopic forks for suspension. Although the way these forks work varies from the basic spring/damping rod-type to high-performance cartridge-type forks, they all rely on a slick oil-like fluid to dampen the fork's movement, held in check by a set of seals. With time, these seals deteriorate, causing the fork oil to leak, which can lead to a loss of control if the oil manages to leak onto the front tire or brakes. Damaged seals exhibit symptoms that are easily found.
Things You'll Need
- Clean rags or towels
- Brake cleaner spray
Clean and inspect the fork tubes, particularly where the lower fork legs, or stanchions, meet the upper fork tube. Run your finger across the fork tube, feeling for dents, corrosion or scratches on the tube's surface. If neither is present, move on to the next step.
Note that this applies to inverted forks that are found mostly on modern sport bikes, as well. However, inverted forks will have the thinner fork tubes on the bottom of the fork.
Compress the front fork by holding in the front brake lever and pressing down firmly on the motorcycle's front end. The forks should compress evenly with some resistance. If the forks compress unevenly, one or both of your fork seals has been compromised.
Release the front brake and reinspect the fork tubes both visually and physically. Run your finger across the fork tubes again. Any oily or slick surfaces are symptoms of faulty seals. Immediately replace those seals.
Inspect your motorcycle's front wheel and tire, as well as the brake rotors and pads. If there is any sign of fork oil leakage on any of these components, clean them immediately using a brake cleaner spray and wipe dry with a clean towel.
Tips & Warnings
- If there are any signs of damage on the fork tubes, such as scratches, dents or corrosion, you may need to replace the fork tube as well to prevent damage to any new seals installed. As a rule of thumb, if a scratch is deep enough to catch a fingernail, it will damage a fork seal.
- For further troubleshooting information, refer to a service manual specific to your model of motorcycle.
- If you do not feel confident that you can properly identify a leaking fork seal, have the motorcycle inspected by a qualified technician.
- If you suspect that your motorcycle has a compromised fork seal, do not ride it until the situation is resolved.
- "The Professional Motorcycle Repair Program;" Professional Career Development Institute; 1995
- Dan's Motorcycle Repair: Front Forks
- Photo Credit Jupiterimages/Photos.com/Getty Images