Which fork seals for 2001 YZ426?


22 replies to this topic
  • jcm3

Posted December 08, 2009 - 09:48 PM

#1

I did a bunch of searches using different wording, but didn't find anything that I could confirm.

Which fork seals are a good replacement for Yamaha fork seals? I have read alot about the Yami fork seals being pretty crappy, and am interested in seals from another make/model that would fit and last longer than stockers.

On the bright side, I learned a hell of a lot about the forks, fork oil, 4x4 when using tie downs, etc. with my searches! :banghead:

  • grayracer513

Posted December 08, 2009 - 11:15 PM

#2

The only OEM Yamaha seals I know of that have recently given trouble are the ones used in the '06-'08 models. These have been upgraded, and have nothing to do with your bike.

If you are experiencing repeat failures:

  • Your inner fork tubes have scratches or chips in them
  • Your bushings are worn
  • You ride in mud a lot and/or let it dry on the fork tubes
  • Your dust seals don't scrape well enough, or you don't clean under them frequently enough


  • matt4x4

Posted December 09, 2009 - 10:37 AM

#3

yeah - the older YZ seals were almost bulletproof - they would last forever.
if you go with aftermarkets like all balls (same as moose) you have to be really careful about what weight oil you use - anything higher than 5 and it'll blow right by the seal because the seal is designed to create less stiction - which is done through a looser fit with differently designed scrapers, however, they will lift right over heavier oils.

  • l_campionero

Posted December 09, 2009 - 10:38 AM

#4

I replaced the fork seals in my 2000 YZ426 probably six times until I installed a set of Moose seals....end of problem.

  • LEMMON1

Posted December 09, 2009 - 10:43 AM

#5

is there a post on how to replace those kinda step by step? my left one went and i need to redo it...my buddy and i did the race tech valves in it years ago but he did most fo the work and im kinda like mehhhhh on doin myself since hes now stationed on the other side of the country

  • l_campionero

Posted December 09, 2009 - 10:59 AM

#6

It's in your service manual. If you don't have one, you can go to yamaha-motor dot com dot au and download one for free.

  • jcm3

Posted December 09, 2009 - 01:31 PM

#7

The only OEM Yamaha seals I know of that have recently given trouble are the ones used in the '06-'08 models. These have been upgraded, and have nothing to do with your bike.

If you are experiencing repeat failures:

  • Your inner fork tubes have scratches or chips in them
  • Your bushings are worn
  • You ride in mud a lot and/or let it dry on the fork tubes
  • Your dust seals don't scrape well enough, or you don't clean under them frequently enough


Actually, no problems with repeated failures yet. I just bought it, and it has been awhile since it was last ridden. The seals are leaking, and it seems like I've read a number of threads where people say that the stock ones didn't last long.

I know that there are things that I can do (like not using the tie downs too hard) to help, but figured if there was another make/model part that worked better that I'd rather go that route.

If stockers are fine, then I'll just order those.

Thanks for any info.

  • l_campionero

Posted December 09, 2009 - 03:29 PM

#8

....I know that there are things that I can do (like not using the tie downs too hard) ....


If tying a bike down hurts the seals, then you'd better not go off of any jumps.

  • grayracer513

Posted December 09, 2009 - 03:50 PM

#9

The idea that tying the bike down causes the seal to leak is silly. Compressing a fork that's designed to be compressed, and probably a good bit more than you do when you tie it down, won't hurt anything. What it may well do, however, is cause a seal that is on the verge of leaking, or leaking only a little, to leak a significant amount of oil during the ride home, giving the fasle impression that that was the whole cause.

Before you replace the seals, though, try cleaning under them by pulling dow the dust seals and running a business card under the seal lip until it comes out clean.

  • Florida_426

Posted December 10, 2009 - 07:48 AM

#10

Original seals still in my 02 426. I clean under the wipers, as Grayracer said, after each race or practice with a piece of film stock and some WD-40 on the tubes so any small dirt particles will be flushed clean. I also check the inner tubes for scratches after the cleaning so I don't tear a seal. I use Yamaha 01 fork oil so it is light enough not to pack up and blow back through a seal.

Bill

Visit the ThumperTalk Store for the lowest prices on motorcycle / ATV parts and accessories - Guaranteed
  • jcm3

Posted December 10, 2009 - 05:34 PM

#11

Thanks again for the info, I had read that tie downs can contribute to fork seal wear.

It just seems logical that if a bike was tied down, the seal would have to maintain a high amount of pressure for a LONG period of time, rather than for one quick jolt as in jumping.

I haven't done any scientific experiements or anything, I'm just sayin...

  • l_campionero

Posted December 10, 2009 - 05:40 PM

#12

There's not that much pressure.

  • grayracer513

Posted December 10, 2009 - 05:45 PM

#13

If you want to believe in the theory (and no one has ever demonstrated that it's more than that) that just holding a pressure far lower than what they are rated at for a few days will cause the seals to leak, then run out and buy one of those $40 gizmos to keep your forks from compressing that are made by the people who promote the theory.

Speaking from more than 40 years of experience, there is nothing to it whatsoever, and that fork can sit there static like that with pressure on it indefinitely without leaking a drop.

  • l_campionero

Posted December 10, 2009 - 06:05 PM

#14

If you want to believe that theory....


Posted Image

I believe JCM 'edited'....

  • grayracer513

Posted December 10, 2009 - 06:37 PM

#15

I believe JCM 'edited'....

So did I, and in that case, I will add that the thing that causes seals to fail IS NOT the pressure they have to hold against, nor the amount of time they hold it. What does them in is wear and physical damage. The wear requires that the forks move, and since, while they are tied down, they don't, no wear will occur to encourage failure. Physical damage is the result of dirt intrusion, or of running the seal over burrs or scratches, but again, this requires motion, and there isn't any.

If simply holding the pressure seems like something that would logically overwhelm the seals over time, then what about pressurized containers? Shouldn't a welding bottle logically start leaking after a few weeks?

  • jcm3

Posted December 10, 2009 - 09:36 PM

#16

Posted Image

I believe JCM 'edited'....



I did, but before anyone replied. I didn't break a rule, did I?

  • grayracer513

Posted December 10, 2009 - 10:49 PM

#17

I didn't break a rule, did I?

Nope.

  • matt4x4

Posted December 11, 2009 - 07:50 AM

#18

I believe the reason people see their forks leak when the bike is tied down is pretty simple:

When tying a bike down, there are other forces at play which you do not have as much while you're riding since while riding the shock is always moving and freely adjusting/absorbing the pressures/stresses put on it to.

When riding, pressure against the front wheel (when landing a jump for instance) is transfered relatively straight up the shock leg - this is obtained through a combination of a freely rotating wheel and the springs.

When a bike is tied down, you get that same pressure from the tie downs pulling the handlebars to floor of the truck/trailer, but at the same time, the tie downs also pull the handlebars towards the front of the box with good force - this force wants to push your fork legs backwards because your wheel is unable to move and roll over that force and that will cause distorted pressure on the seals - pushing the fork leg harder into the seal along the rear edge of the seal, creating a spot with less seal pressure along the front edge of the seal - this is where the oil will trickle through and then it will seep out around your dust seal.

  • grayracer513

Posted December 11, 2009 - 08:29 AM

#19

What you're trying to say is that if the fork bushings are loose enough, and the tie down straps run at at enough of an angle, the inner tube may be pulled either forward or back, off center in the seal, weakening the seal's ability to hold pressure in that position.

Certainly possible, but then the leak at the seal would still not have been caused by tying the fork down in a compressed position. The cause would be worn bushings.

  • matt4x4

Posted December 11, 2009 - 11:13 AM

#20

Yes - exactly - here is always SOME play between the bushing and tube - else it would not be able to ride on a thin coat of oil - once it's static - locked in one spot, not picking up oil every stoke any more, it is easy for the oil to squeeze away between the bushing and wall surface - giving some play - no matter how insignificant it may seem - it is still some play allowing for some movement.

And yes - my whole point was to point out that you could see a leak while tied down but has nothing to do with wearing out while tied down, just that's the moment you would see it and therefore many would assume it is due to being tied down.

Of course - once you release the tie downs, everything should form back to normal and be ok....maybe that's where the other thought comes from to not leave your bikes tied down for prolonged periods of time or you'll cause seals to break - (possible permanent deformation??).

All I can say to that is our bikes tend to spend half a year tied down on a trailer since we hook up and go daily, unless I'm cleaning or fixing them, they rarely come off the trailer so I keep them on it to speed up the time it takes to load up and go. No adverse effects because of it for us.





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