Harold Bawlzangya Racing

Fork Revalve for Woods Riding

I needed some space and had to remove the Restackor charts.  Contact me if you are interested in any of that data.

Final Update:  I sold these KYB OC forks on Craigslist once I had the KYB TC forks installed.

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The factory ’04 KX 125 forks don’t work very well in the woods.  They are very harsh, especially on sections that have a series of rocks, ruts and/or roots.  As far as I know, the ’05 KX 125 forks are identical.  I don’t know if the ’03 KX 125 forks are the same, so I’m not sure how much of this applies to those forks.

Special tools needed for the job

Before I outline the changes I made to the fork, I wanted to show the ‘highly specialized’ tools I used to work on the forks.

To get the base valve off, I made this very precise tool out of a bolt and a nut for a total cost of about $.50.  Home Depot didn’t carry anything that fit, so I had to pick up these metric pieces at an Ace.

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I just put a socket on the welded nut and put the bolt head in the base valve.

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Once the base valve is out, this specialty tool also works well for holding the base valve while you work on it.  I put it in the vice,

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And then place the base valve on top of it.

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Cartridge holder

I made this cartridge holder out of some tubing and a brass fitting I had laying around.  I got very lucky that the shape of the brass fitting fit perfectly in an indentation on the top of the cartridge.  This holder slides over the rod and locks in place.  I usually clamp a pair of vice grips around the tube to get a handle on it.

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Oil level measuring tool

Luckily Bed Bath and Beyond is right next to PetCo near my house.  A syringe and some flexible and rigid air pump tubing was all that is needed to make this fork oil level measuring tool.

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I just measure the level I need and market it with a marker.  When there are too many marks, some carb cleaner takes everything off so I can start fresh.

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As is, the only downside is that you need one hand to hold the rigid tube in the fork at the desired level and then the other to operate the syringe.  I’m sure there is a simple way to make a holder, but it doesn’t seem worth the effort right now.

Seal Driver

Using PVC as a seal driver is pretty common. I used 2″ pipe.  I did relieve the inner edge of the PVC so it wouldn’t catch the lip of the seal.

I clamp the PVC to the fork tube pretty tight and then move the tube up and down to drive the seal into place.

One tool that I didn’t make but has been well worth the money (both from a time perspective and wasted fork oil perspecitve) is Shim  Restackor.

1st round of base valve changes

Actually the first thing I did before making and valving changes was to change the springs in the forks.  I went  from factory – .42 to the recommended .44 fork springs for my weight and type of riding.

Early on in my research, I came across several related posts stating that .15 shims shouldn’t be found in any set of forks.  Unfortunately the ’04 KX 125 forks has the entire high speed portion of the stack comprised of .15 shims.

During my testing and to keep costs down, I tired to use my existing shims and not purchase anything new yet.  I tried at least a handful of different base valve shim configuarations before coming to the conclusion that I wasn’t going to find a good combination with my existing shims and base valve only changes.

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Disabling/removing bladders

As I was testing different base valve changes, I started coming quite a few posts on the various forms discussing removing/disabling the bladders on KYB forks to improve their feel and reduce mid-stroke harshness.  You can either disable the bladder, or remove it completely.  This post will give you a little how-to on removing and/or disabling the bladder.

I decided to completely remove the bladder.

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Once the bladders are off you can tap the spring seat back on the cartridge.

Even with my base valve changes and removing the bladders, I still didn’t like the way the forks felt.

Mid-Valve

I did a lot, I mean A LOT, of reading on how to improve these forks.  About 1/3 to 1/4 of all the posts I found mentioned the mid-valve as the cause of the harshness associated with these forks.  Since I wasn’t having too much luck with base valve only changes, I thought I’d take a shot at changing the mid-valve.

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The stock mid-valve on these forks is a 2 stage stack configuration with quite a bit of lift.  Since it is more time consuming to get to the mid-valve, I wanted to reduce the number of times I’d have to go in there and shuffle shims.  I did some research on Valving Logic to look at other bikes with this type of fork.   What I tried to do was copy the approach used in other stacks while minimizing the changes I’d be making to the factory stack.   I ended up with something not too radical, I basically just made it a single stage stack and reduced the float to .3 mm.

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I rode the bike around with this mid-valve change and the last base valve change and it was clear that I still wasn’t there.

Back to the base valve . . .

I decided it was finally time to break down and get rid of the .15 shims in the high speed section of the base valve stack.

After trying a few things with Shim Restackor, I decided upon a shim stack that maintained an almost factory level of low speed dampening (to keep the forks up in their stroke and to help with bottoming on jumps, g-outs, whoops, etc) while really softening up the high speed.

The easiest change was simply to replace the stock .15 shims with an .10 equivalent.  MX Tech had the best combination of prices and shipping.  I got my shims within a couple of days and the packaging of the shims were excellent.

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After pulling the base valves from both forks, I swapped the .15’s with the .10’s.

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The first of the two graphs compares my latest stack to factory at a high impact.

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 This second graph is set for a low impact.

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After a quick test in the backyard on some 6″-12″ rocks I’ve got laid out, I think this is my best combination yet.  I really need to get out and ride to see what jumps and some g-outs feel like.

I’ll update once I get to go riding and really test this combination out.

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2.24.11 Update:  After two rides with the latest revalve, I’m starting to wonder if I should ditch these KX forks and find something that is better suited for the woods.  I’ve learned alot and made progress, but I’m not confident that I’ve got the best set-up.  I made this post to see if I should try a different set of forks.

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3.3.11 Update:  I made the changes as suggested from the above post and went for a ride this AM.  I can definitely say that this has been the best combination so far, no signs of harshness.

Here are my current shim stacks, I set the oil level at 125 mm.

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The forks are definitely more compliant, but I’d like to see if I can firm them up a bit without reintroducing the harshness.  I didn’t bring any fork oil with me today, so I couldn’t test reducing the air gap.

I doubt that removing the crossover in the BV had that substantial of an impact.  Therefore I think most of the improvement I felt came from increasing the float and making the MV stack softer.

With the factory shim stacks and the slightly heavier .44 springs, I always felt that I was using up too much of the front suspension on the relatively small jumps and g-outs that I encounter.  I recently came across this site that seems to confirm the stock valving has too little LS.   I think I’m going to try one more change to the base valve and possibly go overboard on beefing up the LS stack.  I believe I have 6  .24 shims left over.  I’m going to test putting 3 in each BV and see what happens.

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3.6.11 Update:  Since I’ve been opening up my forks so often with these shim stack variations, I’ve been holding off on rebuilding the forks until I was done making shim changes.  Now that I feel I’m really close, I decided to finally replace the seals, bushings and wipers.  The Pivot Works kit I bought said it would work for an ’04, but the PW bushing on the right clearly isn’t the same as the one from the ’04 on the left.  I’ve ordered new bushings and will have to wait to finish putting them back together.

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I’ve made what will hopefully be the last shim stack change.  I was originally thinking that I’d add three .24 shims to the base valve.  That would have gotten me really close to the factory setting.

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I decided on adding just two .24 shims to firm things up from my last stack, it looks like it will be a good balance between what the factory set-up and my last test ride.

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3.13.11 Update:  The All Balls rebuild kit arrived and the bushings match up.

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I’m using OEM seals.  I know they have more stiction than the SKF seals (but less than others from what I’ve read), but for $10 from eBay I couldn’t pass them up.

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Finally I went with the cheap K&S wipers.

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I’ve never taken bushings out of a set of forks, so I’m not really sure how worn out these are.

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This picture is just for my future reference so I can make sure the aluminum washer is positioned correctly.

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I use electrical tape to cover the sharp edges when sliding the wiper and seal onto the fork tube.  I coat it with fork oil and everything slides over it rather easily.

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I’ve had some questions on how the cartridge holder I made works, so here are a few pictures showing exactly how that fits.

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A 5/8″ spark plug socket fits perfectly into the end of the front axle to hold it in place when tightening the nut down to specs, no need to mess with temporarily tightening the one side of the axle clamp.

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Front end all done, hopefully this will be the last time.

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5.11.11 Update: Shortly after getting the forks put back together I tried out some sub-tanks, that post is HERE.

I recently bought a really nice set of 2004 RMZ250 forks had had been revalved.

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Even though these were from a motocross only bike, I was curious to see what a professional revalve would look like.  After pulling things apart, I was surprised to find the mid-valve unmodified and the bladder still in place and functional.  I cleaned in internals out and left the bladders in place, but disabled them by removing the white plastic ring and removing the spring and check plates.  I’ll start with an oil level of 95mm, which is what was set originally with these forks.  I’ll be putting the sub-tanks on these forks.

The revalved BV had several of the 24.1 shims removed, the crossover was left in place and several of the .15 shims in the high speed stack were replaced with .1 shims.

With this set of forks, I decided I would try the revalved BV stack with one exception.  I pulled a 14.1 crossover they had in place and replaced it with a 24.1 shim.  So this new BV stack looks like this:

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I decided to make a couple of small changes to the MV stack that were in my original set of forks.  I made a change to one of the shims and increased the float by .1mm, for a total float of .4mm.  This new MV stack looks like this:

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11.16.11 Update:  The KX forks are history.  While I made a big improvement over stock, I couldn’t pass up the opportunity to get THESE.

After just ONE RIDE I knew I wasn’t going to go back to the KX forks.

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