Fork Seal Strategy

[BDI]

I have never used anything between my tire and fender during transport. I think that is a myth and there is no way that would stress the forks more then me ridding the bike. The only thing that has ever caused me to blow fork seals premature is the wrong set up.

[dirtjunkie85]

many times you dont need to buy all new seals. just run a tear off around the inside of the seal to dislodge any dirt lifitng the seal up. If seen that work fairly well, although it will not help if the seal is damaged or your lower fork tube has a bur that is tearing the seal.

[Hillclimb#42]

Ok, bought a seal saver. Basically, a waste of money. Well, it did fix 2 bikes before getting ruined. Its too flimsy and folds easily with pressure. I did manage to make my own out of some clear plastic packaging, which is similar to the tear-off plastic that was mentioned.
  I could not fix the 250's forks with the seal saver method. I did get them to slow the leaking waaay down after removing them from the bike, leading me to believe that I had them tweeked in the clamps. I crash alot, and knew I was ridin with tweeked bars, but hadn't considered the forks out of alignment, until Don's suggestion hit me later. What is the best way to ensure the forks are aligned? After looking at it and thinking alot about it, I can only guess that having both forks loose and start with the wheel and axle, and work up the the clamps. Am I thinking right?

  I think you are also right about the lighter 5wt oil being better. 10w is pretty stiff. Adjustments are almost all the way soft to be in my liking. I see that stonger springs and lighter oil could be a solution. Does thicker oil or thinner oil cause more or less pressure on the seals? Does bottoming out or stiff setting cause more pressure? Just trying to understand what's going on, not really looking to set-up suspension solely on seal problems. Thanks for your input as always.

[kaw rider]

you dont what your susp. to buttom out all the time, it works better when its set up for your weight and riding style.

[don46]

First off, the weight of the oil should no impact on seal failure, bottoming out repeatedly will have some effect, not necessarily because of the oil but because you have compressed the air in the fork, the fork extended has a volume of air and lets say it is atmospheric, as you compress the fork it also compress the trapped volume of air and the pressure rises. stiff adjustments will have no affect on the seals other than to say your fork won't bottom as easily and it will minimize the increased pressure in the fork tube. I set my forks up to use the whole travel without harsh bottoming, I do keep the oil changed fairly frequently, have you seen the crap that comes out, and when I do change oil I also change seals and break the fork all the way down and clean everything.

Alignment is important, if the forks are twisted in the clamps, not only does it not handle right it also does not load the fork seal evenly and can lead to premature failure.

On the K5 you unscrew the axle so not much chance of misalignment there, but on the 250 the axle goes throught the lower fork tube with a nut on the opposite side and then 4 pinch bolts this is where I've seen issues, axle gets dirty and doesn't want to go in so they use the cresent wrench to tap it in, this cause a burr on the end of the axle then as you tighten it it pulls the fork tube over causing a side load on the seal. If you have a rider that is sensitive to fork settings they can feel the bit of drag on the fork becasue of the misalignment, I can't feel the difference but have realized the importance of having everything right.

The last thing I will say is that the newer forks seem to leak easier than the older units, the fork manuf. have made bigger and bigger fork tubes and have reduced the surface area of the seal to reduce friction which could leak to premature failure.

[bigbellybob]

every fork is different. i had the 50mm zoks in 97 and they sucked. second ride on a new bike and the seals started leaking. nothing helped the seals leaked almost instantly after rebuilds. i have some 50mm wp's that r very similar to the zoks and they have never leaked.

and not to get into another ATF debate but, i have used ATF in my forks for 10 years now. 

[Hillclimb#42]

and not to get into another ATF debate but, i have used ATF in my forks for 10 years now. 

That stuff must be good in everything  SCARY, man. Where'd ya hear about that?

 Thanks for the info, Don. Thats pretty much my set-up. I look at the forks after riding a bit, and am looking for just a few inches that have not been wiped clean. Got the seals replaced and am hoping to have that behind me for awhile. gonna try to keep them clean, and aligned. That alignment tool deal is funky to me. I looked at a buddies and it seems that you'd have to hold it on the forks up high, then down low, but you'd have to remove the wheel. I'm a carpenter, by trade, but can't seem to find a solid way to measure their alignment with or without a special tool. I pulled the fender and tried getting everything straight looking. I swear, I work on them just as many hours as I get to ride them.  Getting things right means riding with confidence. Thanks for the help...

[Friar-Tuck]

 Hey HC,
The first time I was aware of the ATF in the forks, it was actually recommended in my Honda FSM for my '85 Cr500 & XR600.
  The first time I changed the fluid in them both I used syn atf.  (Got lots of junk out of both sets)
Then went to 7wt. fork fluid.  It worked just fine.  But I'm an old and slow trail rider!
 
  Tuck\o/

[Hillclimb#42]

That seems weird to me. ATF in the forks, a little cheaper, but how would you know what weight you are using, or be sure that its performing right. Foaming or expansion and contraction with atmospheric changes and riding conditions. It would be hard to tell what's goin on inside there, and its expensive parts to replace, if there is an issue. I'm no expert, not even close, is it the same chemical composition? Does the vicosity of ATF, and the oil that's typically used, react the same to extreme temperature swings? Is the FSM like "Factory Support Manual" or something like that, Tuck? Not stoking a debate, just interested in everyone's opinion, to get a good working knowledge of these forks.

  Its also weird that when you dump out the old oil, it looks like used crancase oil or somethin'. What causes it to darken like that? It has to be internal oxidation of parts, don't it? Surely thats not all dirt and grime that passes by the seals.

  What does it do, if you run a higher oil level than standard, or lower? Does it translate into harder/softer or is it just a recommended window of oil capacity levels? Suicyde?


  What is the best method for oil level? Measuring down form the top of the compressed fork, or ratio cup with the recommended amout of ml's? I have been doing both as a double check for my rookie status, but all of the double checking adds to the repair time quite a bit. Thanks for all of the responses, hopefully I am not the only one that needs the education!!!!

[BDI]

Its not just the fact that your bottoming out that kills the seals, It's the speed at wich it happens. The forks blast through their travel way faster then they would other wise and the pressure in the forks spikes very fast and very high. Also in my opinion you should use the fork oil that comes in the bike stock. back in the day forks were not adjustable to the degree that they are now so you would have to change the weight of the oil. Now most forks can be adjusted way to soft or stiff by the clickers alone thus making it pointless to change the weight of the oil. In most cases that I have seen people just create head aches by putting the wrong weight oil in their forks.

[don46]

I agree with Brian it's not the bottoming its the speed at which you bottom that cause problems. I'ved used ATF in forks in the past but probably not for over 20 years, I use either Golden Spectro or Red line fork oil. The golden Spectro is 5wt the redline I have is from 1.75wt all the way to 7wt, and depending on the application depends on the weight of the oil as a rule I would stick to 5wt for the kyb's. On your fork cartridge the is an anti bottoming cone, thats the little silver piece that spins on the cartridge rod, if mates to a tube and together they are the anti bottoming device. A higher oil level has more resistence to bottoming, a lower level conversely has less resistance to bottoming. There are boatloads of parts and fixes for the KYB forks, some work and some don't, many of the later model forks had an oring on the mid valve, replacing that with a spring was a big improvement. They also came with bladders on the fork, many tuners removed them and some didn't.

If you have the ability to revalve your forks you should take the time to get it setup for you, if you don't find a good suspension shop that you can trust. From my experience I would stay away from the big names you don't get what you pay for, small shops usually have the guy that owns the shop doing the work, I used to send mine to Tom Morgan, he did a phenominal job. Surely you would have somebody in your area that was equally good. Maybe you all can chime in and let everybody know who does good work and who doesn't

[bigbellybob]

i was flabbergasted the first time i did the forks on a ktm. the manual  only gives you a air space number and doesn't tell you how much oil to put in. its really easy now that i know what to do. i use a peace of hose from my baster with a o-ring over the hose. you slid the o-ring up the hose tell its at the desired number say 120mm from the end of the hose. then you just hold the o-ring at the top of the fork and suck out fluid tell it wont pull any more out and you have left 120mm of air space in the fork. less oil is smother but will bottom easier. to find a happy spot i start on the low side for oil and then inject 5ml at a time through the bleeders tell i get to the sweet spot 

and as just throwing the ATF out there it has worked for me but i don't expect anyone to try it based on that.

for the dirty oil coming out its mostly from the bushing wearing.

and IMO the best thing to do when setting up you suspenders it to start with the sag. nothing is going to work right tell you set your sag. i find this to be a good right up on setting it. now if i could just come up with the cash to buy some new springs.
http://www.harrymoto.com/MX/RaceSag/set_your_race_sag.htm

[don46]

and IMO the best thing to do when setting up you suspenders it to start with the sag. nothing is going to work right tell you set your sag. i find this to be a good right up on setting it. now if i could just come up with the cash to buy some new springs.
http://www.harrymoto.com/MX/RaceSag/set_your_race_sag.htm

Bob is right there are basics to making your suspension working correctly, all suspension bearings must be in good shape, you must have the right springs with the proper sag set, and generally speaking suspensions are set up for 175 lb intermediate riders so if you fall in that realm you might be good to go. on the 06 250 and up to 05 250f I always used a fork oil level tool, set mine at 100mm, the newer stuff is a bit different, there is the cartridge chamber that is filled seperate from the fork outer tube both are typically measured in ML not in mm of oil level. fresh oil is your friend, not just in the forks, the shock as well, have you ever rode your bike hard and felt how hot the reservoir is change it and keep your nitrogen pressure at the desired set point

[suicyde]

  What does it do, if you run a higher oil level than standard, or lower? Does it translate into harder/softer or is it just a recommended window of oil capacity levels? Suicyde?


  What is the best method for oil level? Measuring down form the top of the compressed fork, or ratio cup with the recommended amout of ml's? I have been doing both as a double check for my rookie status, but all of the double checking adds to the repair time quite a bit. Thanks for all of the responses, hopefully I am not the only one that needs the education!!!!

The fork oil rests on top of the compression shim stack, less oil means a softer initial to mid stroke, more oil, stiffer initial to mid stroke. its a great tuning tool.

most forks from the 90's is measured in mm from the top, with the spring out and at the bottom of the stroke. newer forks like my '09 yz it is a measured amount that is poured in. check your manual for fork oil height and adjustment settings.

[suicyde]

and IMO the best thing to do when setting up you suspenders it to start with the sag. nothing is going to work right tell you set your sag. i find this to be a good right up on setting it. now if i could just come up with the cash to buy some new springs.
http://www.harrymoto.com/MX/RaceSag/set_your_race_sag.htm

Bob is right there are basics to making your suspension working correctly, all suspension bearings must be in good shape, you must have the right springs with the proper sag set, and generally speaking suspensions are set up for 175 lb intermediate riders so if you fall in that realm you might be good to go. on the 06 250 and up to 05 250f I always used a fork oil level tool, set mine at 100mm, the newer stuff is a bit different, there is the cartridge chamber that is filled seperate from the fork outer tube both are typically measured in ML not in mm of oil level. fresh oil is your friend, not just in the forks, the shock as well, have you ever rode your bike hard and felt how hot the reservoir is change it and keep your nitrogen pressure at the desired set point

Yeah My YZ I run at 100-102mm, I hear the new KX really likes 106mm