Blown Front Fork Seals

11 replies to this topic
  • Robert_Brazil

Posted October 09, 2001 - 10:16 AM


After 4 perfect rides on my new WR426-01 (totally stock) I noticed that the oil from the left leg of my front fork had leaked. I have not jumped with the bike and when transported I always use a suspension limiter and never keep the bike longer than necessary with the suspension pulled. There is also no visual damage to the fork, neither have I crashed the bike. How is this possible? This morning I brought the bike to my dealer :-( and noticed that the right leg is also leaking (slightly), I don't know if this is the same problem or simply because the right leg had to carry all weight impact during my last ride (also no jumps, just woods). Anyone knows why this happened? What should be changed, any recommendation on hints (when serviced) are highly welcome.

  • Sean_McCutcheon

Posted October 09, 2001 - 11:56 AM


I been having problems with my seals also. I was told to use Factory Connection seals and so far they are holding up pretty good.
WR's seem to have a problem with leaking seals, epecially from the factory.

  • Grum_from_Oz

Posted October 09, 2001 - 01:12 PM



Hello. The solution to your problem is more than likely an easy fix.
- Remove fork guards.
- Use a thin-blade flat screw driver to gently pry open the dust cap.
- Slide the dust cap down the fork tube.
- Slide a piece of photographic film between the fork tube and the fork seal.
- Gently work the film in a continually downward motion around the leg. This will ensure that the dirt/grit that is causing the seal to leak is removed.
- Clean out dust cap. Fill with Lithium grease.

That is the method I use on my '99WRF and am still on the originally seals! No leaks!

Keep it on the back wheel.


  • MX_Tuner

Posted October 09, 2001 - 02:27 PM


A business card works well also, instead of a piece of film. I've fixed quite a few seals this way.

The problem is dirt getting in under the seal.

MX Tuner

  • Robert_Brazil

Posted October 10, 2001 - 08:31 AM


[QUOTE]Originally posted by Grum from Oz:

Thank you for the response I'll try to fix it. I just have a doubt, the bike has an upside down suspension, in the step by step description, you say "DOWNWARD move between the leg and the fork seal" the fork seal is the dust cap, that I slid down? I suppose not. Isn't there another step that after removing the dust cap I have to try to get out the actual oil seal down? The Lithium grease is to "glue" any future dirt?

Thanks for your reply.

  • MX_Tuner

Posted October 10, 2001 - 01:11 PM


You don't remove the oil seal. Once you pry the dust seal down, you'll be able to see the oil seal. Now take a business card or a piece of film and slide it under the seal lip and slide it around the fork tube. You're trying to clean out under the seal.

The grease will hopefully let the new dirt stick to it instead of getting wedged in the oil seal.

MX Tuner

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Posted October 11, 2001 - 03:29 AM


Mark is Da Man.....This past saturday my right fork seal started to leak and Mark had me clean unser my dust cap, Sure enough the leak stopped.....If the WR seals were weak I would have blown them long ago with all the stress I put my ride under. Two Years of violent abuse on the forks and they're still going strong....The only reason I'm getting ready to rip my forks off my ride is so that MXTuner can make my WR withstand even bigger jumps......

Bonzai Posted Image

  • wpattison

Posted October 11, 2001 - 06:49 AM


kayaba's design is the problem. it's been a problem for at least 6 years, but nobody - especially not the magazines - will talk about it. the seal cleaning tricks work good in the field while the forks are on the bike and you have no choice, but there is a better long term fix. when the stock ones blow, buy new seals and tighten the garter springs - both of them. then yank the forks apart and do the same to the dust wiper garter springs. reassemble. another helpful item is the bleed buttons that can be had from white brothers for about $15. you need a bit of machine work to install them in the fork caps, but being able to let the air out at a touch is very handy when tying the bike down.


will pattison
racer, engineer

  • Robert_Brazil

Posted October 11, 2001 - 10:57 AM


Thank you all for the feedback provided. I just came from the dealer and unfortunately there is a very tiny almost invisiable dent (?) on the fork cilinder (stone impact likely), albeit almost invisible it is noticiable when one passes a finger nail. The dealer says that this damaged the seal and he suggests to change the seals and polish the surface with sand paper. What do you think?

Two questions remain: (1) the dealer has two kinds of fork oil;
Motul Comfort light 2.5W-5W and;
Spectro SX 400 5W,
which oil is best?

(2)Secondly, I weigh 178 pounds (81 kgs) without gear, which oil height is recommended for riding in the woods (no jumps, although I also don't like a too plushy front fork. The stock oil hight seemed quite right. What do you suggest? Thanks a lot for the advice!

  • MX_Tuner

Posted October 11, 2001 - 01:22 PM


Don't use sandpaper to clean the ding. Use a fine toothed file. Sandpaper will remove metal around the ding. A file will only remove the ding.

I'd use the Spectro 5wt and set it at 100mm.

MX Tuner

  • Woodzi

Posted October 12, 2001 - 01:49 AM


Sandpaper will work if you use a block and very fine grit sandpaper - 800+. I have also had success with a fine sharpening stone. Either way be careful to remove only enough material to remove the burr that is damaging the seal.

  • GPS Dual Sport

Posted October 16, 2001 - 10:01 AM


When the WR and YZ 400F first came on the market back in 1998 some of the early production units were produced with very slightly undersized fork tubes. Seals were leaking on the ride home from the dealer. Yamaha was making warranty repairs on the customers you complained the loudest.
It won't hurt to check your fork tubes with an accurate micrometer to make sure they are not undersized.
old guy and GPS geek


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