The top of a fork leg is closed by a cap or plug that holds the fork spring under pressure. When it is released, it can fly out and hit the face or chin. This page covers how forks are usually closed and how to open them in a controlled way.
Safety
- Wear eye protection and keep your face away from the line of the leg.
- Never open a cap while the leg is held by the bike only at the top. The spring has a lot of stored force.
- If you do not know how your fork is built, stop and ask a workshop.
Two common designs
- Screw cap. A threaded cap on top of the leg. It is sometimes also the part that clamps the leg to the top bridge on bikes with no top pinch bolt, so it is under load as soon as it starts to turn.
- Push-in plug with a circlip. The plug is pushed down against the spring and a clip in a groove holds it. When the clip comes out, the spring pushes the plug up.
Steps
- Loosen the pinch bolts at the top and bottom bridge so the leg can move. If the cap is a screw cap that also holds the leg, loosen it a little before you release the pinch bolts, with the leg still supported.
- Hold the leg firmly. Turn a screw cap slowly and keep a hand over it as the last threads release. Stop if it fights you, and check that nothing else holds it.
- For a plug with a clip, push the plug down against the spring with a tool or with a helper's help. Pick the clip out of its groove and then let the spring raise the plug slowly. Keep your hand over it.
- Lift out the spacer, washers and spring in order. Lay them down in that order so they go back the same way.
- Pour out the oil into a pan.
- On refit, push the plug or cap down against the spring in the same slow, controlled way, and fit the clip or start the thread by hand to avoid cross-threading.
Check your work
- The cap is square in its seat, not tilted.
- The clip is fully in its groove all the way round.
- The leg is tightened in the bridges to the value in your bike's manual.
If it did not fix the problem
- The cap or plug will not move: do not force it. A workshop may have the right holder.
- The oil came out dark or milky: Replace fork oil and seals.