99' yz 400 suspension blows

9 replies to this topic
  • ETS

Posted April 18, 2000 - 06:49 AM


My 99' sucks in terms of suspension, it is harsh feeling. It transfers everything to my wrists on impact. I'm coming off a 96' rm250 that had great suspension to me, it was plush yet didn't bottom much where the yz is stiff yet still bottoms fairly easy. I've played with the compression and rebound settings on the shock and fork, but I haven't played with springs or oil height. I've never had a whole lot of luck with oil height anyway, but I was wondering if anybody has had their suspension re-valved or if gold-valves would be as good as sending my suspension away. I weigh 170 in gear and ride all kinds of michigan terrain and tracks. Any help or tips would be appreciated.

  • Chris_in_the_Mojave

Posted April 18, 2000 - 07:11 AM


My '98 has had both ends done by Race-Tech by the original owner. I never got to ride it "stock", I can tell you that it was very "plush" when I got it. It had the stock springs with gold valves and 90mm of US-1 Race-Tech oil. The original owner was a 170 lb. fast Vet Expert. I rode the bike as is for several months, it was TOO plush for MX at my weight(225) but really nice for play riding. As I got faster I started bottoming both ends off jumps so I ended up respringing for my weight and used Race-Tech setup recomendations. The bike is very "firm" but not harsh, bottoming isn't a problem anymore.

For starters, I'd go on to racetech.com and run through their suspension set up program. See where you are compared to where they say you should be(springs, oil, clickers). You can change springs and oil yourself and see if that helps. If you need more then you could go for Gold Valves...

Chris in the Mojave
'98 YZ400F

[This message has been edited by Chris in the Mojave (edited 04-18-2000).]

  • GNCCYZ400

Posted April 25, 2000 - 06:52 PM


I have a '98 400 and just retooled the forks with gold valves and the dampening valve adjustments (very important). Like you i'm 175lbs but I race gncc. I needed a suspension that is plush in the woods but wont bottom when on the motorcross section. The gold valves are great!!! very "soft" in the woods.
I did have a problem with bottoming the first time out, but a few clicks in and no more bottom. I have stk. springs (44 for the 98, i thing the 99 has 46) with 95mm oil height.
I did the install myself, but if your not 100% shure of your abilities I'd let Race Tech do the install. Talk to the guys at Race Tech, they are up front and very helpful. I wouldn't trust my suspension to anyone else.

  • ETS

Posted April 26, 2000 - 06:48 AM


Did you only do the forks with goldvalves? What do you mean my the "dampening valve adjustments"? Is that a modification to the dampening circuits? Mine just sucks and I don't have a lot of time to fiddle with it. I seems bad enough getting away a couple times a week to ride it. I can install gold valves though, I've done seals and oil changes many times. I guess I'm looking for the whole package to be balanced and smooth. Thanks for your help and I will probably call race-tech.

  • GNCCYZ400

Posted April 26, 2000 - 06:13 PM


The dampening valve has a "mid-valve" on it that actually creates compression damping where the rebound check plate usually is. The removal of this valve will make the valving much more consistent and the ride more plush. Unless you are a very aggressive pro or a supercross racer you should remove this valve and replace it with a standard check plate and cylinder seal plate (both come with the gold valve). This modification only effects the compression not the rebound dampening.
The install will take longer than most people tell you. I'm very competent with my skills and tools and it took me 6 hrs for one fork. The other went much faster (I knew what to do)only 1 1/2 hrs. There are "special" tools that you must have, like a cartridge holding tool (I made one out of a piece of 1" sch 40 pvc), in-lb torque wrench, and a propane torch to loosen the loctite on the dampening cartridge. To get to the dampening valve you have to remove 4 "indentions" in the cartridge tube. If you drill more than 2mm into the tube you can toss your forks and buy new ones because you will have drilled into the seal head and the cartridge will leak. It sounds harder than it really is, if your carefull. The directions and video that come with the gold valve are pretty good but the video shows how to install the valve in a showa fork and just touches on some points on the kyb. The instructions are very detailed but need to be read a few times before you begin. (If you have access to a fax machine send me and e-mail with the # and i'll fax a copy of my directions to you. Be shure to put something in the subject field to "catch" my attention).
I haven't done my shock yet I've got a race this weekend and didn't have time to finish.
All this sounds pretty "technical", but if your good with your hands and can comprehend the directions you shouldn't have any problems. And it is worth the time spent in the garage and not on the track.
Hope this helps,

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  • Jeremy_Wilkey

Posted April 29, 2000 - 01:46 PM


You might actually be surprised at would happen if you leave the mid-valve in. The Mid-valve believe it or not actually lets you do more with the valving. The mid-valve is branded as a "evil" but in reality it lets you run much lighter compression valve settings and still get bottoming resistance. The best way to remove the CV is to use a mill. It's very hard to control the depth of the drill, and still sufficiently remove the peen.



  • DaveJ

Posted May 04, 2000 - 10:18 AM


My 426 has been a handful since day one. Mostly front-end high compression (fast hard hits) problems. I can dial out the compression for the bumpy trail rides, but then it handles poorly on the track and/or large jumps. Doing so also doesn't seem to resolve the trail riding problem, it just makes the ride easier on the wrists. The hits are absorbed, but the front end remains sloppy. Even with a dramatic increase in damping (by the way, it's "damping", not "dampening").

I took mine to Lindemann Engineering for re-valving. Much better, but the last ride revealed that I still have a ways to go. I'm having a hard time getting to the "firm-but-soft" feeling you get when all things come together.

So nothing to contribute other than that. Misery in companionship. Perhaps I'll try the gold valves that you're speaking off. If this or something else works out I'll post what I find.

  • Airastro

Posted May 04, 2000 - 10:35 AM


I just had my suspension redone on my 426 by Pro Action Suspension. They have a shop in the FMF factory. The complete revalve took only two days and what a difference. I also went heavier on the springs front and rear. The difference is unbelievable. The bike now soaks up the little hits with no harshness or feeling at all. The bottoming resistence is great also. I came up short on an uphill step up and thought oh SH*T, but the front absorbed the hit and I really never even had to let off the gas to recover- continued straight ahead. I think the plushness is most represented in how long i can ride for now without arm pump. I am the king of arm pump, and I did 2 25 minute motos with only about a 20 minute break in between and still felt great. this was on Glen Helen's National track which they are beefing up for the big race.

To me this is the most important money you can spend on your bike. The suspension will make you much faster than adding a pipe will for the same cost. The only negative is the suspension doesnt have the cool factor of an aftermarket pipe.

  • Tim

Posted May 04, 2000 - 12:23 PM


How much would this revalving cost, including springs? A bunch? How about just new springs in the front? Anyone try this yet? I think I am going to get some stiffer ones for the forks.

  • DaveJ

Posted May 06, 2000 - 08:29 PM


I spoke with a Race Tech guy on Friday and at Sears Point today. They have their gold valve kit and a delta valve kit. The gold valve allows high compression setting via shims, only accessable by removing the valve. The delta valve (an entirely new assembly) allows external adjustments of both high and low compression. However, they said that for fine tuning, working the shim stack on the gold valve is best. In other words, the external high setting on the delta valve is "course". They also recommend a 5 weight oil, (I now forget what factory is). I believe, however, that it is possible to remove the valve, adjust the shim stack, and replace it without having to remove oil or preload, (assuming you have to turn the fork upside down). Let me know if any of you have done this.

Their catalog also has a chart for determining spring rate. You select the spring by your weight (without gear) then add or subtract for particular bike types and usage. Their example is for a 160lb rider on a XR600 that works out to a .409, with .005 and .015 added for the displacement and engine type, (perhaps some one can enlighten me why 2 verses 4 stroke and high displacements effects the required spring rate). Final result, a .430k spring rate. One factor not considered was their recommendation to add .02 for AMA Pro style riding. That would put the 426's .46 rate about right for a 150 to 160lb aggressive rider.

Let me know if you guys have thoughts on all this. I'll most likely give the gold valve a try, keeping my options as open as possible for on-site tuning.

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