KYB No compression or rebound

[Quantumcanuck]

I have a kx250 2003 model with the stock kyb's up front. It occured to me one day that neither of the clickers were making any difference at all. I completely disassembled both forks and cleaned everything perfectly incase there was debry holding valves stacks or needle valves open.

After assy I put fresh 5wt oil in and it appears there is still no compression or rebound adjustment. The forks are not in the bike, I am just pushing down on them with my arms and feel/see no differnce between full out or full in on either clicker.

The O-ring on the base valve is fine and the needle valve assy in it works fine. I'm wondering if it is the catridge valve assy at the very top that is letting too much oil get by or is it the seal around the mid valve assy?

It appears to me that if I take a screw driver I can move the mid valve from side to side every so slightly while it is in the tube. Is this a normal tolerance or is its sealing surface worn?

Either way, where can I buy rebuild parts for the mid valve or the cartridge valve? My Kawy dealer wants me to buy a complete assy at over $400 smackers :(

Anything else I am missing?

Thanks

John :ahhh:

 

[WhiPit]

Did you disassemble the cartridge the first time? In other words, did you clean any debris from the mid-piston? If not, there's your problem. I think the mid-valve shims warp on that fork as well - which will require replacement.
Also, you can't buy just the top of the cartridge (the seal), so be careful.

 

[Quantumcanuck]

Yes, I completely disassemled the forks the first time, including the mid valve assy and cleaned it.

How can I tell if the mid valve shims are warped? They look flat and appear to sit flat and entire seal the mid valve.

What about the fact that I can see side to side play of the mid valve assy in the catridge tube? It's a small amount of play but it is there. I'm thinking that the seals on the nid valves are worn allowing oil to blow by them. Is this common for these to wear and need replacement?

Thanks again

John

 

[WhiPit]

If the shims are flat, you're okay. If they're warped, you'll know - it's pretty obvious.
I doubt the side play you see if affecting anything. It takes quite a lot to wear out the piston bands on those mid-valves.

 

[Quantumcanuck]

ok, so what should I be looking for as the reason that I have no ability to adjust compression or rebound damping? Both adjusters seem to be working fine. Could it be the cartridge valve?

Thanks again

John

 

[WhiPit]

Does (or did) the cartridge tube ID look worn when you had it apart? When did the problem start? Are you the original owner, or was some one possibly into the forks before you? You say everything appears to be in working order, but obviously we're missing part of the puzzle.

 

[ActiveRide]

I can't imagine both sets of adjusters not working. Are you actually riding the bike? Or just doing a in the shop test? If for some reason both aren't working you should check the midvalve piston band. If this were to be so bad that neither adjustment worked you would of had a hard time bleeding the air into the cartridge so I doubt that's your problem. You did bleed your catridge right? (fill the fork with fluid, grab the catridge rod and pump up and down until the rod moves fluidly through the entire stroke). I don't mean to insult your intelligence but you never know. The clicker adjustments work on oil flow. So if you don't feel any resistance when you pump the rod that's the only way they are not working. It's hard to imagine both sets of forks having a problem.

Try riding the bike when making the adjustments. It can be really hard to tell the difference when the forks are off the bike espiecially the KYB stuff. They seem to have less effective low speed adjustments than the other brands.

 

[Quantumcanuck]

Well, when I first got the bike it was rock hard. I turned out the top rebound adjuster and all of a sudden the front end felt super springy as I pumped the front with my arms. This is why I think I should be able to feel a difference when pumping one fork by hand in my garage. There was a night and day difference while on the bike from creeping back up to bouncing back up. As I started to learn more about suspension and what the clickers are for I wrongly decided I wanted 2.5 weight instead of 5 (I was after plushness). After a few weeks I learned more and got faster and was bottoming on hard landings. I turned the compression in bit by bit and tested eventually turning it all the way in to no avail so back to 5wt I went thinking the 2.5wt was so light it was rendering my adjusters useless. More riding and more learning I started to notice that it didn't mater how much I turned the compression in, I couldn't feel any difference and I still bottomed on many landings, big and small landings, and hard! Then I realised that (it seemed) there was zero difference in rebound feel between full in and full out on the clicker. Not at all like the night and day difference when I first got it.

So here I am trying to repair them myself because I had a little run in with Leukemia almost 2 years ago and have not been able to work since, so money is tight (incase anyone thinks I'm a total cheap-o and begging for free help lol).

I can see that I might not feel any difference in slow speed compression because I'm just not able to pump them fast enough with my arms. But can it be the same with rebound? And at the track I sit on other bikes and pump the front and it feels so plush and smooth with a pronounced rebound effect making it come back smoothly and controlled. You can feel the damping in both directions doing its job of absorbing motion.

When I changed oil I did pump the rod and remove all the air in the cartridge tube assy.

What I want to know is if the mid-valve piston bands actually are a common replacement part because of wear. Mine are smooth with no scratches in its surface but like I said, while in the damping cartridge tube I can make them move from side to side with a long screw driver. It's a very very small amount of side to side but it is there. Do these things actually wear out? Is there any where else I should be looking at?

Thnks again guys.

John

 

[WhiPit]

I'd have to agree with Active....if the cartridge bled out okay, I doubt it's the piston bands.

I know it's a hassle, but try putting the forks back on the bike (and the wheel) and see what happens. Does it feel like there is only a spring in the fork, like an old Caddy with worn out shocks? Or can you feel any damping at all?

 

[Quantumcanuck]

Everything is back together. There is damping effect in both directions but the clickers seem to make zero difference. Even the back of my bike is controlled and smooth, especially the rebound. The front doesn't feel like it has nearly enough rebound damping. I swear when I first got it there was a night and day difference that you could see, let alone feel in rebound. I have ruled everything else out.

As for purging the cartridge of air. The side to side play I am on about is small. The oil I coated the mid-valve with for reassembly would seal it enough to pump air out - but during high pressure oil situations I can see it allowing enough blow-by to lesson damping in both directions.

I'm just going to change the bands to see. This is driving me nuts.

Anything I should know about getting these bands and chaging them?

Thanks guys.

John

 

[WhiPit]

I think it's pretty difficult to get just the piston bands for those pistons. If you have a source - great. But for the average guy, they aren't available.

 

[KTM-Lew]

Did you ride the bike after reassembly or are you still doing the "garage" test?

 

[Quantumcanuck]

I have not ridden the bike properly, just around some small trails by my place but I know I have the exact same issue with lack of damping and damping adjustability. The front is nothing like it was whens I got the bike 2 years ago. As for feeling a difference in rebound just pushing with your arms, you should. I was on two different bikes this past weekend. I turned the rebound to full in and full out and there was a very pronounced difference in rebound effect just sitting there and pushing on the bars. So now I know I'm not going crazy and I did see a huge differnce when I first got the bike and backed of on the rebound clickers.

And now that I have learned all about the valves (even the cartridge valve has shims in it, or mine does anyway) I have deduced that it is most likely my mid-valve piston bands. Damping is effected in both directions so it makes sense considering the lower valve and shims are fine, sealing properly and not warped, the shim stacks on the mid-valve are fine and nothing is stuck in the cartridge valve shim stack keeping it open. All seals are fine also. So, oil is getting by too easily somewhere and I strongly suspect it's the piston bands. I don't see anywhere else that could cause this problem.

I found this in an article - "Check the piston band by placing it back on the shaft with a nut and sliding it into the body. The band should compress and provide a significant stiction to the body wall. If it is lose, or moves too freely then the band and o-ring should be replaced. Simply slice the old band off and install new o-ring and band."

Now that article wasn't about my particulair KYB's but it does directly address my concerns about the free play I have been on about all this time that I see with the mid-valve. And yes, you can easily get mid-valve piston bands for replacement. I have found a couple places on the net that supply them. They cost from $25 to $30 each from what I have seen so far and are easily ordered.

So, this is my next step and I shall see if I get my adjustabilty and damping back. I'll keep ya's posted.

Thanks for all your help guys :)

John

 

[KTM-Lew]

I replied on TT. Are you certain you have the caps bottomed correctly on the cartridge rods? How many clicks do the rebound adjusters have?

 

[Quantumcanuck]

Yes, I backed out the rebound adjusters before I threaded them onto the rods then brought the nut up to tighten against the cap. I think that's how its done.

John

 

[Quantumcanuck]

I also just recently found this.

"QUESTION 15: WHY CAN’T I JUST CHANGE THE OIL?
The best analogy is to think of worn fork internals just as you do of worn clutch plates. When the clutch starts slipping, a change of gearbox lube isn’t going to keep the clutch from slipping for very long. It takes new plates, springs and, possibly, a clutch basket before clutch action returns to the same level of performance as when the bike was new. When hammered on the track, your forks oscillate wildly, heat up to over 100 degrees and put serious side loads on the shims and piston seals. All these parts need constant R&R."