QUICK FORK SEAL REPLACEMENT
You’re loading up your bike in the morning and there it is: the dreaded oil puddle. Maybe it’s only under the left fork leg, or maybe it’s under both. Either way, blown fork seals can ruin your plans. But, it doesn’t have to be that way. If you’re prepared, you can do a quick fork-seal change in under half an hour. If you carry the right tools and an extra set of seals, it can even be done at the track. Here’s our in-house fork nerd, Pete Murray, showing us the quick-and-dirty way to change seals without having to do a full fork rebuild on current Yamaha KYB forks.
Remove the fork legs the normal way. There’s nothing tricky here; just the axle, eight pinch bolts and two brake caliper bolts. So far, we’re only five minutes into the job.
Clean out the bottom of the fork. Hopefully, you don’t have any damage here. Zip-Ty Racing sells a protector that can save your fork legs for the next time you have to do the same job.
If you have a vise, great, but don’t clamp the fork tubes directly. Grab them loosely by the foot or the brake mount and remove the base damper-rod bolt.
Now you can break the jam nut lose while you hold the damper rod still. Remove the base bolt.
Take off the dust seal and the seal retainer with a small screwdriver. You’re about 10 minutes into the job now.
Now you will be able to separate the upper and lower tubes by working the fork like a slide hammer. Hold the fork upside down while you do this so that no oil escapes. This is the difference between doing a quick seal replacement versus a full rebuild. You won’t replace the oil.
Set the upper fork tube aside in a safe place where it can’t tip over and spill. Now, remove the bushing and seal from the lower tube. Look for any abnormal wear on the bushing.
Yamaha fork seals don’t really need a reason to leak, but inspect the fork tube for nicks anyways.
If you see or feel a bur on the fork tube, sand it gently with a fine emery cloth or 600-grit sand paper. Don’t overdo it.
To install the new fork seal, use a plastic bag to prevent damage to your new seal. The bag that the seal came in will work.
Now, put your bushings and washer back on the fork tube after you’ve cleaned everything up.
Pull up the damper rod before you slide the tubes back together. Make sure that the jam nut is screwed all the way down before you install the base bolt. It should be bottomed out.
Sometimes it can be a little tricky to line everything up so that the damper rod pops out.
Now pull out your handy fork-seal driver and wrap it around the fork leg. Drive the seal into place with three or four firm strikes. You’ll feel the seal hit bottom. Time: 20 minutes.
Replace the seal retainer and the dust seal.
Now you can tighten things up. Using the slot in the fork-cap-ring nut wrench to hold up the damper rod, tighten the base bolt to the jam nut. Make sure that the base bolt is fully bottomed out on the rod before it touches the jam nut. Then, bring the jam nut up to contact the base bolt. Finally, torque the base bolt to the fork tube. For most current Yamaha forks, the torque is 55 Nm or 40 pound-foot. Now, put the fork on and go ride! Net time: 30 minutes.
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