Fork Mid Valve

5 replies to this topic
  • Hick

Posted August 09, 2000 - 02:33 PM


My forks are due for servicing and I have two questions:

1) I'm a decent mechanic when it comes to trucks and other equipment but I've only been riding for two years, so many areas of moto-mechanics still spook me. Like my forks. I'm perfectly happy with the shop who services my forks currently but wonder how difficult it really is. What does this involve? What tools do I need? How badly can I screw them up (this is really the most pertinent question)?

I have read my manual and a few tech articles in mag.s but I'm looking for some insight and advice from fellow Yamaha owners.

2) I was told that the next time I serviced my forks to be proactive and replace the midvalve with an aftermarket one. Is there anything wrong w/ stocker? Any improvements to be had w/ aftermarket? Will all aftermarket midvalves affect performance or are some made just to rectify weak stocker?

I'm no speedster but I'd say I'm a pretty aggressive rider (guy who services forks agrees just from looking inside my forks). I'm 6'0", 175 lb.s and run the ocassional off-road event in the desert (sand washes, sand whoops, deep braking bumps but few rocks) and my play riding is essentially the same. I love my forks in deep whoops and like them everywhere else but maybe I just don't know what I'm missing. Can I make my forks work better?

BTW, this may be a faux pas but the bike is a 426 and not a WR, but I figured fork internals are the same. The YZ side doesn't get even half the response as the WR side of thumpertalk.

I guess this post (and my bent rotor post) qualifies as a vote to combine YZ/WR forums.

As always, all advice appreciated...

  • Kevin_in_New_Hampshire

Posted August 09, 2000 - 05:24 PM


Did you read the September issue of MXA?

Forks are quite easy to service, IF YOU HAVE THE RIGHT TOOLS. The big thing you may need is the damper rod holding tool. The tool you have to have is a seal driver.

If you want some advice, send your suspension off to get re-valved and re-sprung if needed. After that, do everything yourself. The difference between stock and modified suspension can be unbelievable!

99 WR, all YZ mods, de-octopused, OEM YZ tank and IMS seat, jetting by Clark/James, got forked by Pro Action, DSP airbox, PB Header, Stroker SX-1 SA, Thumper Rad Guards, Acerbis Hand Guards, WAITING IMPATIENTLY FOR MOAB, boning up on my sheep shearing skills AND knowing Mitch will help me out IN ANY WAY I NEED IT!!

  • John_in_Long_Beach

Posted August 09, 2000 - 05:24 PM


I just changed the fork oil last week. I it was a piece of cake.

As for changing the valving. I have had not had any experience with that, however I can tell you that I am much happier with the fork action after going with a 100mm fork oil level instead of the 135mm.

It sounds like you do similar riding to me, (38 years old 170lbs medium to aggressive trail riding and a little MX). I think the forks are significantly improved. Before, in my opinion, the forks felt like a pogo stick, way too much travel both on compression and rebound, the higher fork level is a nice compromise between a YZ and the mush bucket stock WR.

I have ridden a 426 and my bike now feels like a slightly softer version of a YZ, whereas stock the 2000WR forks are way too soft.

I wanted to try the fork oil level first because I wanted to see if I could tune the forks to my liking before spending $300 having them professionally valved. I think I can say that so far I am satisfied. I have yet to get MX'ing, so that may yeild different results. But I think I will be able to stiffen them up enough for that. And I didn't really want a full on MX suspension, more like something that could through the adjusters work for both.

Hope that helps.

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  • James_Dean

Posted August 09, 2000 - 06:49 PM


See there is an active topic in the suspension category by Jeremy Wilkey called "Kayaba Mid valve", it is well worth reading. Give Mace a pat on the back for his detailed critique.

  • DaveJ

Posted August 09, 2000 - 09:46 PM



It all depends to what level you want to service your forks.

At least, I would recommend disassembling the forks to effectively inspect all seals and bushings and rid all old oil and debris.

I don't think you'll want to rip apart the damping rod (aka compression cylinder) unless you have plans to modify the mid or rebound valve or seal head.

Be cautious using solvent since it can either attract moisture of leave residue.

You'll most likely need or want an air impact and/or damping rod holding tool. One or the other or forget about doing the job yourself.

And you'll need a 14mm allen tool for the compression valve.

I'll stop there. If you are serious about doing this right, and/or want to modify the valving, perhaps we should chat over the phone.

You can reach me at the following e-mail.


  • Bill

Posted August 10, 2000 - 02:28 AM



If you go to the profiles and email Jeff Shearin he has done his forks with the Race-Tech gold valves.

I have sent some questions to Jeremy at MX-Tech and he was very helpful. I have also read the test in MXA on YZ forks. They said they had never heard of MX-Tech prior to the test but rated their forks number one. MX-Tech told me $235 for each end of the bike.

There is a link on the links page to get to the compant or Jeremy.


86TT225, 98CR80, 99WR, WR timing, throttle stop trimmed, air box lid removed, White Bros head pipe, silencer and air filter. Odometer and headlight removed. Moose hand and mud guards. YZ stock tank and IMS seat. Renthal Jimmy Button "highs" and Renthal Soft half waffle grips. AMA, SETRA.


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