Front Fork Seal and Bushing Replacement

Thanks to Ed (FJR Pilot) for this detailed explanation on what to do for your front forks.  I just followed his procedure last week to completely rebuild my forks and I referred back to his information more than the service manual:

Posted 17 September 2011 – 07:26 AM

One of my fork seals crapped out during the NERDS ride this year and started leaking oil pretty bad. I tried the “film hook” trick to clean it out, but it didn’t work, so I needed to replace the seals. Dean (DJB) was kind enough to loan me his fork seal driver tool which he had brought along to NERDS for possible use at Tech Day. Having this tool, I figured that was all I needed, so I ordered all the parts and proceeded to tear the forks apart. Some advice; If you are going to take your forks apart to replace the seals, don’t try to cheap out and skip ordering new bushings. Even if your bushings are perfectly fine before you start, they will likely be wrecked by the time you get the forks apart and they’re not that expensive. Order all three bushings for each side (lower, middle, and upper).

I had about 22K miles on the original bushings and the lowers were definitely showing signs of wear. The Teflon coating was completely worn off on one side down to the metal.
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I didn’t take any pictures of the disassembly process, but it goes like this.

Put the bike on the center stand and jack up the front so the wheel is slightly off the ground.

Take the front wheel and fender off the bike.

Loosen the upper pinch bolts that are holding the very top of the fork legs by the caps. Use a 24mm wrench and loosen the fork caps. Just break them loose, don’t take the caps off at this point. If you take the forks off the bike before you loosen the caps, you’ll have a bitch of a time holding the fork tubes while you try to loosen the caps. (ask me how I know this…) :unsure:

Loosen the lower pinch bolts and slide the forks down and out of the triple clamps. Getting the lower pinch bolts loose can be somewhat challenging. I ended up using an allen bit on a 3/8” socket wrench handle with a piece of pipe on the handle for more leverage. It’s very tight, but you can get them loose without tearing the front fairing off the bike.

Now that the forks are off the bike, back off the preload adjuster, rebound damping knob (at the top), and the compression damping adjustment screw (on the fork leg) until they are all the way out.

Unscrew the top cap from the fork tube. Don’t worry, it’s attached to the damper rod assembly inside the fork and won’t go flying anywhere when you unscrew it from the fork tube.

Use a 17mm wrench on the preload adjuster and a 14mm wrench on the nut below the cap to loosen the nut and then unscrew the cap from the damper rod assembly.

Carefully pull the long thin damper rod out of the damper assembly and set it aside where it won’t get bent.

Remove the nut, spacer tube, washer, and spring from the fork tube.

Dump the old fork oil out into a drain pan. Pump the damper rod assembly several times to help get the oil out. It’s best to let the forks sit upside down for a while to let the oil drain out completely.

The easiest way to get the damper rod assembly out of the lower fork leg is to use a 26mm, ½” drive, 6-sided socket welded to a piece of metal pipe. Using this tool to hold the top of the damper assembly, it’s a simple matter of loosening the 8mm allen screw in the bottom of the fork leg and you’ll be able to pull the whole assembly out the top of the tube. Make sure the aluminum cup at the bottom of the damper assembly comes out as well.

Here’s a picture of the tool I made to hold the damper assembly. The pipe is ¾” x 16” long. I welded a cheap 26mm ½” drive socket to one end and an old 3/8” extension to the other end so I could put a socket wrench on it.
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Once you have all the guts out of the fork tube, the next step is to separate the upper tube from the lower fork leg.

Gently pry the dust cover off using a small screwdriver. It should come off fairly easily.

Use a very small screwdriver to pop the ring clip holding the oil seal in place out of its groove.

Now for the fun part… The Yamaha shop manual says you should fill the fork with oil, put the cap on and use a large press to force the oil seal out. Sounds like it would work, but I don’t happen to have a large hydraulic press in my shop (yet). So, an alternative way to separate the tubes is to clamp the bottom of the lower fork leg in a vise (make sure to use some wood blocks or something to protect the aluminum from damage from the vise) and then just repeatedly attempt to forcibly slide the upper fork tube out of the fork leg. Each “whack” of the upper fork tube on the seal will bump it out slightly. It will probably take the first few slides to dislodge the middle bushing before you will actually have any effect on the oil seal. Don’t get frustrated and give up if it doesn’t come out right away. Keep at it and it eventually will pop out. Using this method will get the forks apart but will also most definitely trash the Teflon coating on the bushings so you will need to order new ones. You may find that the upper tube gets “stuck” when you try to slide it out. This is caused by the bushings sliding partially inside each other and wedging the tube inside the fork leg. Just gently tap on the top of the fork tube using a wood block and a rubber mallet to free the tube and try it again. I found that it seems to work better with smaller, shorter strokes, rather than big “as hard as you can” strokes.

Once you get the fork tubes separated, remove all of the loose bushings, washer, and seal from the tubes and clean everything out thoroughly. The washer will likely be slightly cone shaped from the force of the bushings slamming against it. It is supposed to be completely flat so you should use a new one when you put things back together.

Don’t try to take the black plastic guard off of the top of the lower fork leg. You don’t need to remove it and you’ll likely mess it up trying to get it off.

Here’s all the parts you’ll need for a Gen-II (The Gen-I may have a different parts list)

(You’ll need 2 of each)
4SV-23135-10-00 METAL, SLIDE 2 (Lower Bushing)
3P6-23135-00-00 METAL, SLIDE 2 (Middle Bushing)
4SV-23125-10-00 METAL, SLIDE 1 (Upper Bushing)
4SV-23115-00-00 GUIDE, COVER UPPER (Washer)
4SV-23145-01-00 OIL SEAL
4SV-23156-00-00 CLIP, OIL SEAL (Ring clip)
4SV-23144-00-00 SEAL, DUST (Dust seal)

Total cost from is $58.10 (+shipping)
(You’ll also need 2L of fork oil)
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Once I had everything apart and cleaned up, I realized that I had no way to reseat the new middle bushing that lives about 4” down inside the lower fork leg. Because of the way the forks have to go back together, you need to be able to slide the middle bushing down between the upper tube and the lower fork leg and seat it in its groove. This is impossible unless you have the right tool. (which I didn’t).

Looking down the fork leg you can see where the upper and middle bushings are seated. The lower bushing attaches to the bottom of the upper fork tube.
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I figured that I needed a piece of relatively thin-walled metal tubing that was exactly the right diameter so that it would slide over the upper fork tube and inside the lower fork leg. Amazingly, I found the perfect sized tube at the local Advanced Auto Parts store for $8.99. It’s a chrome exhaust pipe tip.
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Here’s a closeup of the label.
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The exhaust tip has a rounded end and screws to hold it on to the exhaust pipe that need to be cut off in order for it to slide in where it needs to go to seat the bushing. I marked the tube and carefully cut off both ends. The length is not critical. Just cut off enough to make it a straight smooth tube the whole way.
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Here’s the tube with the ends cut-off.
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Make sure you’re careful when you cut the ends off so that you have a straight end that’s perpendicular to the tube (not at an angle). A straight end is important to make sure the bushing is seated correctly and not at an angle inside the fork leg. Take a file and some fine emery cloth to the cut-off ends so you don’t have any burrs or sharp edges.
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Before you start reassembling the forks, slide the exhaust tip down inside the lower fork leg until it rests on the top of the groove where the middle bushing will go and make a mark on the tube at the top of the fork leg. This mark will give you an idea of how far you have to push the bushing down into the fork leg until it’s fully seated.
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Make sure that the upper fork leg and the lower fork tube are completely clean before you put things back together. When I took mine apart, there was all kind of crud down in the bottom of the fork leg.

Slide the middle bushing onto the upper fork tube and install the lower bushing in the groove at the bottom. Lube everything up with fork oil.
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Carefully slide the upper tube into the lower fork leg and let the middle bushing slide down until it hits the top of its groove. Slide the exhaust tip down over the upper tube and inside the lower fork leg until it’s resting on top of the middle bushing. You’ll see that the mark you made on the tube earlier is now about ¾” above the top of the fork leg. That’s how far you’ll need to push the middle bushing down until it is fully seated.
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On one of my fork legs, I was able to just use the exhaust tip to push the bushing down into place. I just slid the exhaust tip tube up and down and used the weight of the tip itself to tap the bushing into place. You can tell when it’s fully seated by the sound it makes when you tap it and it’s against the bottom of the groove. You can also tell by looking at the mark you made. It should be level with the top of the fork leg.
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The other fork leg wasn’t quite as cooperative and needed a little “encouragement” to fully seat the bushing. I used the old metal washer from below the fork seal and a piece of 2” PVC pipe slightly longer than the upper fork tube along with some gentle taps from a rubber mallet to push the bushing down into place.
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Once you have the middle bushing seated, the rest is easy. Slide the upper bushing down over the fork tube and press it down into it’s groove using the exhaust tip. Make sure it’s all the way down. It should look like this.
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Next, put the washer in.
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Next is the oil seal. Be sure to lube up both the inside lip of the oil seal and the outside of the upper fork tube with plenty of fork oil. CAREFULLY work the oil seal over the top edge of the upper fork tube and then slowly slide it down the tube to the lower fork leg. The inner lip of the oil seal can be easily damaged so take your time.
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This is where the fork seal installation tool comes in handy. It makes easy work of pushing the seal down into place in the lower fork leg.
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If you don’t happen to have an actual fork seal installation tool, you can substitute a piece of 2”PVC pipe. It works nearly as well for pushing the oil seal into place.
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You need to make sure that the seal is all the way down so that the groove for the ring clip is fully exposed.
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Next, install the ring clip in the groove to hold the oil seal in place. Make sure it’s fully in the groove all the way around.
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The last thing to install is the dust seal. I was able to push these into place just by using my fingers. They should slide in fairly easily.
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Now that the seals are all done, the rest is pretty straight forward. Put the aluminum cup on the bottom of the damper assembly and use the “socket on the pipe” tool to carefully slide the damper assembly all the way into the fork tube until it bottoms out. It’s much easier to do this if you have the forks sideways rather than up-and-down. Put some locktite on the bottom 8mm allen bolt and start threading it into the damper assembly. Slide the upper fork tube in and out a little to make sure everything is lined up correctly and then tighten the allen bolt using a torque wrench to 25 ft/lbs.

Fill the forks with the correct amount of oil. Make sure you pump the damper rod multiple times to get all of the air bubbles out so the oil level can be correctly measured. The oil you use and the level you set it at are suspension tuning adjustments that will likely differ from person to person so I’m not going to tell you what to do here. There are numerous other threads on the forum that talk about suspension adjustments that you should refer to if you’re not sure. Or you could just ask our resident suspension expert, Jeff Ashe. He worked his magic on the valves and springs in my forks and I must say, they are way, way, way, better than the stock setup now. I highly recommend his “HaulinAshe” fork upgrade. :yahoo:

Install the spring, washer, spacer tube, and nut. For now, just screw the nut on as far as it will go by hand.

Slide the long thin damper control rod inside the damper assembly and then screw the cap on to the top of the damper. Screw the cap on until it bottoms out. Just finger tight, don’t force it. Then turn the nut back up into the cap and use a wrench to tighten it against the cap.

Slide the upper tube up and screw the cap on. Don’t bother trying to tighten the cap yet. Just screw it all the way on by hand. Re-install the forks on the bike. Tighten the lower pinch bolts to hold the fork tubes, tighten the cap using a 24mm wrench, and then tighten the upper pinch bolts.

Put the front wheel and fender back on, re-adjust the pre-load, compression, and rebound settings back to where you had them and go ridin’.


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1 Response to Front Fork Seal and Bushing Replacement

  1. Luis says:

    Thank,s good job 100 %

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