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WP open chamber fork seals and valves

Rsquared

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Last summer I re-sprung the forks and shock on my bike for my weight. It did the trick to prevent my bike from bottoming out on jumps and G-outs, but my bike went from plush to rather harsh on the forks. I was able to adjust my rear PDS shock with rebound and compression to my liking and my forks were fair, but far from plush. I ended up with the compression adjustment (valve bypass) alot further open than I wanted which pretty much takes the compression valve out of the circuit. So on sharp edges, roots and rocks the front end would deflect.

On my last ride I had a fork seal go out and thought this would be a good opportunity to adjust my shim stack, allowing me to close off the bypass (compression adjustment) and put my valve back in the picture. Typically, if I can catch a leaking seal early, I can use a goggle tear-off to slide between my fork seal and the fork tube to clear any sand causing the leak. I'll probably get some Seal Savers next time I order from Rocky Mountain.

Disclaimer: I’m not a suspension expert, photographer or story teller, but I’m more than willing to learn new stuff, even the hard way occasionally. I don't own alot of specialty tools, so I improvise at times.

I figured since these are open chamber, cartridge forks used on most of the KTM EXC’s and XCW’s, that I’d post my low-budget suspension tuning and fork seal change to share with the group and I’m open for tips and suggestions….

I won’t go thru pulling the front wheel and caliper, and I’ll start with loosening the fork cap.

I pull the handle bar clamps to allow the fork-cap tool to fit under the bars. The reason is that I use the bottom triple tree clamps to hold the forks while I break the caps loose with the fork cap tool.

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Be sure to loosen the top triple tree bolts first, before trying to break the cap loose. Use only the bottom triple tree bolts to hold the fork while loosening the cap.

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Finish stripping the forks by removing the lower fork guard, bushing and cap for the compression adjustment screw. Then clean, clean, clean… (I use cheap brake cleaner)

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Open the rebound and compression settings all the way. (counter-clockwise) If you’re just replacing the fork seals, make note of your rebound and compression settings.

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Finish unscrewing the fork cap.

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Always measure and mark distances and orientations so that it goes back like it was.

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Next break the fork cap loose from the cartridge shaft. Be careful not to booger-up the threads, this can be done by taping the jaws on the chanel-locks. (This stuff is’nt atomic-tight and does’nt need to be going back together)

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Pull the spring and drain the oil.

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I secure the fork leg in a vice, using a rag to protect the finish.

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Next remove the compression valve from the cartridge. I use an impact because you can’t hold a backup on the cartridge, (stop cringing) I adjust my impact’s choke down so low I can almost stop it with my hand. This allows the speed of the impact to remove the valve without the cartridge spinning.

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Then remove the rebound adjustment rod from the cartridge shaft.

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To disassemble the valve the threads have to be straightened out from being peened over.
Note: the valve doesn’t need to be disassembled to replace the seals.

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The shim stack contained 5 main shims, along with numerous step down shims. Utilizing the SWAG method, I determined removing 2 of the main shims should be close to where I wanted to be. We'll see, my first ride feels pretty good over tree roots with my compression at 18 clicks.

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I re-assembled the valve and peened the edge to prevent the nut from backing off. Make sure the nut goes thru the check valve plate and doesn’t pinch it. Go easy this is soft aluminum. Also inspect the O-rings on the valve and replace if damaged.

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Be sure the check valve moves freely.

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Now for the seal replacement. Remove the dust cover and the spring clip that holds everything together.

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Using the inner and outer fork tubes like a slide hammer, just tap them apart.

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Inspect the bushings and replace if they show wear. I have very few hours since mine were replaced and they still looked good to me.

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They make a seal-bullet to protect the new seals during installation, but remember earlier when I said this was low budget… I use Glad-Wrap instead, plus a little grease on the new seal to protect it during installation.

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Then washer, outer bushing and inner bushing.

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Put the inner fork tube into the outer fork tube.

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Use the seal driver to drive the new seal into place, install the spring retainer, and the dust cover.

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Install the cartridge. Important: use your fingers and feel inside to make sure it bottoms out in the lower fork tube.

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Next comes the compression valve. Use the impact, choked back, then torque at 35 nm.

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Don’t forget to put the rebound adjustment rod into the cartridge. Push down on it and it should move freely with a little spring resistance.

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With the top fork tube bottomed out, add the oil. Don’t let any oil get into the rebound adjustment rod hole. Then raise the top fork tube 10” to 12” while holding the bottom fork tube with your feet, cover and seal the tube with your hand, then push down to pressurize the oil into the cartridge. Add oil and repeat the process until bubbling stops appearing around the cartridge.

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Raise the cartridge up and down to check for resistance both directions. This will verify all the air is out.

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With the top fork tube bottomed out, set the oil level. I’m running 120mm.

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Raise the cartridge and thread the spring over the cartridge until it’s all the way down into the fork.

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While still holding the cartridge up, compress the spring to expose the threads to screw the fork cap on to.

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Carefully snug it up.

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Screw the cap into the top fork tube.

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Before putting the forks back on, return the compression and rebound settings to where they were, put the fork guard bushings and fork guards back on. Slide the forks back into the triple clamps and snug the bottom clamps only.

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With the fork cap tool snug up the fork cap.

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Now set the forks where you want them in the triples and torque them up. Set the spring preload, I’m at 2 turns. Install the handle bars and torque the clamps, and mount the front wheel and torque.
Then the final most critical step of the whole process. Clean the caliper bolts, apply Lock-tite and torque 25nm.

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Pump up the front brakes, check your work, go ride.
 
I'm glad you posted this (I'll have to finish reading when I get home) because I noticed the other day one of my fork seals is starting to leak.
That being said I'll be tackling new seals sooner or later. Did some mention a KTM tech day recently? :trust:
I did seals on my old xr400, the the KTM looks way more complicated.
 
I'm glad you posted this (I'll have to finish reading when I get home) because I noticed the other day one of my fork seals is starting to leak.
That being said I'll be tackling new seals sooner or later. Did some mention a KTM tech day recently? :trust:
I did seals on my old xr400, the the KTM looks way more complicated.

If I can do it i'm sure you can. I have a driver you can use also.
 
Excellent!

"Disclaimer: I’m not a suspension expert, photographer or story teller, but I’m more than willing to learn new stuff, even the hard way occasionally. I don't own alot of specialty tools, so I improvise at times."

I think your photography and story Tellin' was first rate.
Let us know how your adjustments feel. Then we can comment on you being a suspension expert. ;-) But for me, if there is no fluid on the floor the next morning, I call it good! :thumb:
Thank You for this, there are alot of us out there running these OC forks. Sam
 
I do this sort of thing all the time, but it was really nice of you to post the pictures and a brief description so anyone can have a go at it.. Thanks for taking the time to post this.

Gray
 
I've been beating the internet like a rug looking for exactly this information. Should have known. THANKS! (again) Roger.

I'll be out getting dirty now...
 
Help! I replaced the oil and fork seals on my 2005 exc OC forks using this excellent tutorial, however, on one of my forks, after reassembling everything, the rebound adjustment knob doesn't stop. It just keeps turning. What am I missing? Any help would be appreciated. I called TJ's and the suspension tech said it was probably something wrong with the screw cap (top of fork where clicker knob is). I ordered a new screw cap and still have no adjustment stop either way. clicker just keeps going.
 
Sent you a pm with my number easier to explain rather than type. There is a video somewhere. I'll try to find it.
[ame="https://www.youtube.com/watch?v=glG3gUjxjEU"]How to Set WP KTM Husaberg Fork Oil Level - YouTube[/ame]

Here is some text I stole from another forum.
"The nut you put the spanner on when you pull the spring down needs to be screwed further down the thread so the the boss with the rebound adjuster on, can screw further down the thread. You will need to engage the plastic bit back into its slot on the rebound adjuster cap first, and turn the cap until it with draws the plastic needle all the way back up the inside thread on the boss. Tighten the nut back up to the boss, release spanner and spring. It should now be ok, just try before put all back together.
Hard to explain, but hope it helps. "
 
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I think Gary nailed it. Let us know if that takes care of it. No fear, it's something that can be taken care of.

Sam
 
I think Gary nailed it. Let us know if that takes care of it. No fear, it's something that can be taken care of.

Sam

Yep, Gary nailed it alright. I failed to make sure the nut on the damper rod was all the way bottomed out so when I installed the fork cap, it wasn't going all the way down on the threaded part of the damper rod. :doh: That video link helped tremendously and the following quote that I found on a thread on thumper talk:
"
Before you install the fork cap.

Push on the rebound tube in the middle of the damper rod. It should feel spring loaded. If not, the rebound needle is gummed up.

With the fork cap in your hand, turn rebound knob CCW until it stops. You may have to hold the pin that goes into the rebound tube.

On the damping rod, Make sure the plasic spring guide (hydralic stop) is screwed all the way down until it lightly jams in place.(This is where my problem was, as Gary suspected)

Then screw the fork cap onto the damping rod until the cap is fully seated. The damping rod must be bottomed out into the cap.

Holding the spring guide 22mm nut with a wrench, continue turning the fork cap CW. The spring guide will break lose and will thread itself up the damping rod. Continue until the spring guide jams itself against the fork cap.

Then screw the cap into the upper tube.

If you don't do it like this, your rebound knob will just spin and not do anything."


After I got the fork back together, I pulled the other fork off that I had done previously, and sure enough, I hadn't bottomed out the nut on the damper rod on that one either. Now both forks are back together and the rebound adjustment knobs are working fine. :clap: Sometimes, I can't believe how thick headed I can be when it comes to mechanical issues. Thank God for this forum!
 
Awesome. Don't be to hard on yourself, I was quick to answer for a reason.
 
Help! I replaced the oil and fork seals on my 2005 exc OC forks using this excellent tutorial, however, on one of my forks, after reassembling everything, the rebound adjustment knob doesn't stop. It just keeps turning. What am I missing? Any help would be appreciated. I called TJ's and the suspension tech said it was probably something wrong with the screw cap (top of fork where clicker knob is). I ordered a new screw cap and still have no adjustment stop either way. clicker just keeps going.

Incredibly poor advice from a suspension tech at a major KTM shop. The open chamber forks have not changed in basic design for over a dozen years (they have been incrementally improved several times though). Screwing down the spring guide to make sure enough threads are exposed so the cap bottoms and the rebound adjuster works right is as basic as it gets. It is even explained in the WP suspension manual for open chamber 48mm forks.

Good that there are guys here to give solid advice. Very nice.
 
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