'99 WR400 - Suspension Help


You refer to the cartridge assembley being fully disassembled.. are you refering to the seperation of the damping rod in the slider?

I have removed the damping rod from the fork, after removing the base valve, and have actually removed the nut holding the valving on the mid valve assembly. you can get to the Mid valve using this method. I assume you are taking the damping rod apart to get full access to the Mid Valve, right?

If I do remove the shims on the other side of the valve, does the washer thickness have to equal the shims removed? thanks for the help.



After viewing the Damping rod assembly. here are my observations.. It would appear Yamaha used 4 small punch marks at the top to permanently hold the assembly together and to keep it from screwing back out.. are these punch marks drilled out and then you unscrew the top off to remove the Mid valve assembly?? or is there another method to remove to get full access to the Mid Valve?

I usually do all my work on the bike, as I have been riding for about 25 years (street) and working on engines for the about the same length of time.. so go ahead and throw the procedures at me, I can handle it... thanks for assistance.


Okay, you asked for it.

The four peened ares need to be drilled but not through the wall of the cartridge. All you're trying to do is relieve the stress put on by the peening. So you'll only be drilling about 1 or 1.5mm deep. Tap around the top of the cartridge with a small hammer to help loosen the loc-tite the factory uses when assembling the parts. I have a split circular holder that insures I don't crush a tube in teh vise. What I have done in a pinch is re-install the compression adjuster assembly in the tube and wrap it with sandpaper folded so both sides are rough Now carefully tighten the vise and loosen the top of the cartridge. Once you get this loosened, you can pull the guts out. Now you'll be able to see the mid-valve on the back side of the rebound piston. You'll need to get a check plate that is the same outer diameter as the largest shim. What can be done is simply removing the narrower shims in the center of the mid-valve that hold the larger shims and the check plate apart. This will work in accomplishing the same thing as removing all the shims and using a single check plate. Questions might get answered quicker if you e-mail me directly.


MX Tuner

MX Tuner,

Can you recommend a website/book/magazine article that has fairly detailed explanations of the internal workings of the fork & shock on our bikes?

I haven't decided what I'm going to do yet. I'm trying to gather enough info to make an educated decision.



I don't know of any sites that go into that type info at all. There may be some but I haven't run across any. But then again, I haven't looked for any.


MX Tuner

MX tuner:

Thanks for the information.. I would love to talk tech with you... what is your email address..

mine is 1gearhea@gte.net


MX tuner:

OK, drilled, but not thru... and the top has been removed and mid valve is out... I used an interesting method to apply torque to the top of the head.... instead of squeezing the tube in my vise... I inserted a phillips screw driver through the large bleed holes at the bottm where the base valve goes.. and this kept the tube away from the vise.. I then used the screw driver in the vise, loosend, and applied torque to the top, with my twisting at the top the screw driver turned and held in the vise and allowed me to apply greater torque on the top. walla... it loosened... I have removed mid valve.

now.. can I disable the mid valve using your method earlier?? I have one large washer at the bottom, then 3 smaller on top of that, then followed by 4 larger washers with one smaller on top next to valve body... are you indicating to remove the 3 small diameter washers only and install the remaining??



Can't vouch for Eric's Book, but it may be the best $$ spent to learn ALOT more about repair!

I will be buying one with my big bore kit this fall.



How is sunny CA, my friend??


[This message has been edited by NH Kevin (edited October 17, 2001).]

Kevvie baby,

I have an earlier edition of Eric Gorr's book but I can't remember how detailed it got on the internal workings of the forks & shock. I'll try to find out if the new edition has any specific info on the KYB forks w/mid-valve.

Sunny CA is wonderful as ever - actually praying for a little rain before this weekend. We're taking our Patio Hauler (about the same as Polo's rig) on it's maiden voyage this weekend up by Tahoe. We're meeting up with a bunch of folks from DRN - should be a great time regardless of the dust. What's this you're saying about moving to Wisconsin? I keep waiting to hear you say you're coming to CA smile.gif


When you buy a set of Gold valves a great fork maintenance/Gold Valve installation video comes with it. After MXTuner rebuilt my suspension while I watched, I went home and watched the video....Can you say Dejavu?

WR-JASON.....Sorry dude but either someone has blown sunshine up your butt or you just don't ride hard enough to know the know the limits of your WR suspension. I have been riding since GA426OWNER was the guest speaker at the last supper. When your riding ability and aggressiveness reach a certin level (Or weight in some peoples cases) things bottom out often and cause great pain and distress. You cannot compensate for that with more speed. actually more speed means more pain!. Valving can make things much better and more comfortable.

MXTuner: Suspension seems to be Spot On! Went to the nex MX track this afternoon in Luthersville. 45 foot double....smooth as silk. 25 ft Table Top and the 40ft with no problems. Step up jump with flat landing zone.....No problem. Even got lazy a couple of times and landed front wheel low....DID NOT BOTTOM OUT....I immediately stopped and checked the sweeper 3.5 inches of travel remaining (Great!) Changed rear shock to 10 out on the rebound and on the compression. Not kicking as bad to the right now. Boost rebound to 12 mabe?

Can't wait for the woods this Saturday....this should be awsome....If the front end sticks as good as it did this evening, I'm going to kick some butt in the woods.....

Thanks Dude...

Bonzai grin.gif


1999 WR 400F:

Headlight Removed,Odo Removed,Gray Wire - Cut,Throttle Stop - Trimmed,YZ Timing,GYT-R Pro-Bend Hand Guards /Tripple Clamp Mounts,YZ Front/Rear Fender,YZ Number Plate,Race Tech Suspension(by MXTuner),Dunlop 756 Front and Rear,Renthal Fat Bars W/GYT-R Pad,Renthal 14/53 Gearing,DID Race Chain

Custom Grips,Graphics by CEET,White Brothers E-Series Exhaust,Modified Compression Release,Acerbis Frame Guards

MS, my e-mail address is mxtuner@mindspring.com

Bill, if it is still kicking in the rear, you need to go stiffer with the rebound. You may have the rear spring set so stiff for your weight that it may be overpowering the rebound valving in the shock. Try going two clicks stiffer at the bottom of the shock. Glad to hear you like the forks. They should soften up considerably (over shapr edged bumps) once all the new rubber parts break in some.


MX Tuner

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