terry hay

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Nov 8, 2003
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As I pulled down my first set of Bladder forks from a preproduction KX250 back in August 99 I was curious as to what the maker had intended when he unleashed this modern wonder on an unsuspecting market. At first I thought this was Kayabas attempt at making a "poor mans" dual chamber fork. I was later informed that it was designed to create a speed sensitive air spring similar to that of the sub tanks. The forks were essentially divided into upper and lower sections by two forms of seals at the top of the cartridge. On small (low speed) demands oil/air was supposedly able to bypass the seals, compress the bladder and give the illusion of a greater air volume. On high speed demands the seals were to present enough of a restriction to halt the transfer and create a high oil level feel. Whatever it was supposed to do it didn't exactly appeal to the masses. People complained of deflection, harshness and arm pump.
When testing new bikes if we wish to make a simple change to the compression stack we will turn the whole bike upside down and using an air impact wrench remove the base valves, make the change and ride straight back on the track. This allows the rider to evaluate the change while the previous setting is still fresh in his mind. After a short test session with the new KX we decided to do exactly that. Imagine my surprise when I pulled out the base valve and got showered in oil. Pressure had built up in the lower portion of the fork and air and oil was rapidly exhausted as I removed the valve. Now this was while the fork was fully extended and naturally pressure could only be expected to build even further as the forks were compressed. No wonder they had problems with harshness and deflection. Honda decided also to use the bladder forks on their CR125. After discovering the shortfalls of the Bladder Fork Honda continued to use the product only minus one of the seals. This completely negated any possible advantages of a speed sensitive spring. This didn't stop Honda from using the Bladder Fork in their sales blurb in an attempt to lure unwary purchasers. At least they had solved a problem. We had been performing similar mods with the KX shortly after its inception. Enter the KXF250. After a short stint with the much maligned cylinder valve Kawasaki have opted to head back to the bladder fork for yet another attempt at shooting themselves in the foot. One has to question "How many toes are left on the Jolly Green Giant"? Kayaba have attempted to solve the pressure build up problem in the forks by installing a check valve at the top of the cartridge. When pressure in the top portion of the cartridge exceeds that of the lower, the valve will open and equalise the pressure within the fork. It would appear it is upside down. The pressure still builds up in the lower cartridge area. Any attempt to reverse the valve however would see the system fail completely as oil would escape from the lower cartridge area much easier than it could get back in. After battling with the gremlins of this design for two days I decided to remove the seal from the top of the cartridge to see if this was still the fault of this fork. Well you can imagine my contempt for Kayaba as the rider came back with a grin on his face from ear to ear. Still, I guess this is a step forward however; It's a lot easier to remove the sealing band than it is to replace a cylinder valve. Good Luck
Regards
Terry Hay
 

steve125

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Well put terry! :thumb: Thats what I have found with bladder forks also. I think it's best to remove the bladders and throw them in the trash!
 

terry hay

Member
Nov 8, 2003
200
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Steve
I don't remove the bladder. I simply remove the seal and the fork operates like normal. Maybe ten years from now people will be removing a black congealed mess from the bottom of their forks, cursing me all the while.
Terry
 

Rcannon

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Nov 17, 2001
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Terry, do you have a website? If you dont feel comfortable posting it here, maybe you could e mail me with the information. I really enjoy what you post.

jamesc4085#msn.com
 

marcusgunby

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Jan 9, 2000
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I removed the bladder as well as the top seal, seemed to ride nice afterwards, air gap i think i set to 120mm , this was on a KX125 04.
 

terry hay

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Nov 8, 2003
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RCannon
I don't have a website at this stage but we are woking on it. I've never really been into computers and my girlfriend is starting to get the sh-ts with how much time I've been spending on this forum. I really enjoy disscussing suspension with you guys. I only discovered this while trying to contact Eric Gorr and have been hooked ever since. Hurts your eyes after a while!!
Regards
Terry
 

marcusgunby

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LOL terry a few tips from a expert , get a good chair-im on my 5th, get a TFT monitor as these a nicer on the eyes, get a broadband connection as it makes surfing faster, on the girlfriend i have no answer-been trying to train mine since Jan 2000 and she still throws stuff at me:(
 

steve125

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Terry I feel if you remove the seal and just leave the bladders "in" you will loose two things in the process. One:with the bladders out, you will have increased the oil capacity and thats got to be a good thing. Two: by just removing the seal you have effectively just lowered the oil level height during low speed fork action. I don't feel this changes bottoming resistance, but it does soften the early mid stroke as the bladder is in the process of collapsing. With just the seal out the bladders are still working, that can't be good. Thats why I just pitch the bladders and the seal and set the forks at a normal oil level.
 

terry hay

Member
Nov 8, 2003
200
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Steve
My intended purpose in removing the seal is simply to remove the barrier that divides the fork and allows the flow of oil/air to function as normal. The volume of air within the bladder is still subject to the same compressive forces as the rest of the air within the fork. By removing the seal we have eliminated the high/low speed effect the manufacturer intended. With the bladder in place we run the normal oil level for that design which I believe is 90mm. Without the bladder I would compensate by reducing the height. I think we are both achieving the same result with different methods. But you are right and certainly removing the bladder would allow you regulate oil heights with a known volume. I'm curious as to what you thought when you first saw these forks apart? As I mentioned in the post that I thought at first glance Kayaba was attempting to produce a cheap dual chamber. My initial conclusion based on this assumption was that the system was bound to fail due to the fact that the damper rod was not sealed against the top of the cartridge. Oil was bound to escape more easily from the lower portion then it could get back in and we would end up with an emulsified mixture within the cartridge. After I was informed about the "speed sensitive" air spring I had to re-evaluate but still came to the same conclusions regarding flow. In order for the speed sensitive air spring to work effectively I believe we would need to allow a bit more oil to bypass the seal around the cartridge. This could perhaps be achieved and made adjustable by a replacable bleed jet similar to that of a two stroke carb main jet, positioned in the spring seat at the top of the cartridge. Any thoughts?
 

steve125

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Oct 19, 2000
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Terry, with the forks apart and in theory, it all looks good. But as you know on the track it's a different story. With the RB (restrictive barrier) washer removed the mid spike was gone, but the forks dived too much. After the Bladders were also removed and oil level re-set, the forks had a firmer and more progressive feel. I know of a RT dealer that has tried drilling the RB washer with little or no success. IMO the best way to go about all this is the Enzo canisters!
 

terry hay

Member
Nov 8, 2003
200
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Steve
I have never used the ENZO cannisters and I am unaware of any positives or negatives of this concept. I know the Kawasaki team over here tried them this year and then decided to do away with them. Regarding the bladders creating dive I'm a little confused. If the total air volume is identical in both situations then the pressure differential between extended and compressed should also be identical wether the bladders are in place or not. My ideas regarding a bleed jet are not something I wish to commit to practice. Just a concept for fixing something that doesn't work.
Regards
Terry
 

Jeff Howe

Member
Apr 19, 2000
456
1
I think I may have been the original dissenting, doubting Thomas of the bladder on this forum. Argued with Jer more then once and got my butt chewed for calling them a gimmick here. I have been pulling them out and throwing them in the trash for quite awhile. They have made little sense to me since their inception. I tried working with them at first as everyone else did but I got tired of them in hurry.

I'm glad to see somebody else shares my opinion of those wretched pieces of scrap. Oh, and just for the record AGAIN...I also think the bumpers are subpar. I do find these more acceptable to work with though, but I'd take a properly toleranced hydrualic cone any day over the bumpers.
 

terry hay

Member
Nov 8, 2003
200
0
Shocknut
As I mentioned in the cylinder valve post, I believe the bottom out bump rubber gets a bad rap. The fault in the cylinder valve forks is not so much the type of bottom out system, but the fact that it reaches the bottom out system in the first place. If you are keen to try them I will happily send a set of our cylinder valve replacement kits, This will advance KYB fork technology forward to 1997 and be a major improvement from their latest configerations. You will have to revalve the base valve to suit the new oil flow rate. This will allow you to evaluate the merits of the bottom out bumper on its own without the detremental effects of the cylinder valve.
Regards
Terry Hay
 

steve125

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Oct 19, 2000
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Originally posted by terry hay
Steve 
Regarding the bladders creating dive I'm a little confused. If the total air volume is identical in both situations then the pressure differential between extended and compressed should also be identical wether the bladders are in place or not. 

Terry it is my understanding that with the RB washer and seal "in" it in effect separates the two chambers, upper and lower. That is untill the pressure from under the RB washer blows (mid spike) :scream: . This being the case it's easy to see why the forks dive more with the RB washer out and even more so with the bladders left in.  Now you have a single chamber with a bladder collasping making the oil level even lower, untill the baldder is done collasping. I feel this all happens very early in the forks stroke. :confused:
 
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terry hay

Member
Nov 8, 2003
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Okay
And there is where the confusion lies. I'm talking about the bladder being in or out after the seals have already been removed where you are talking about the difference before and after the removal of the seal. Cool!
Catch you later
Terry
 

terry hay

Member
Nov 8, 2003
200
0
Steve
One other point. If you take the bladder out without adjusting the oil height to compensate for the volume being displaced by the material volume of the bladder (minus the trapped air volume) you will naturally have to add some oil. By leaving the bladder in place and simply remove the seals, the air/oil volume remains the same. (Minus the volume of the seals). Granted the overall effect from the fork now will be one that deals with no pressure trapped in the lower chamber allowing the fork to compress easier but this should be attributed to the previous problems associated with the design. Certainly we made need to balance the forces to get them where we want them but once again I can't attribute this to the bladder. I am prepared to stand corrected though.
Terry
 

dbrace

Member
Oct 30, 2002
277
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I also agree that the bladder fork is not a step in the right direction. I normally remove the restrictive barrier. A correctly set up mid-valve is the next step to success IMO.
 

marcusgunby

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Jan 9, 2000
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Im starting to wonder about steve, he keeps buying these bikes with bladder forks and then removing them, then he sells the bike.

Now maybe hes using the bladders for some unconventional uses?? maybe leg warmers? or maybe something else hmmm

 :laugh:
 

steve125

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Oct 19, 2000
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Originally posted by terry hay
Okay
And there is where the confusion lies. I'm talking about the bladder being in or out after the seals have already been removed where you are talking about the difference before and after the removal of the seal.

I guess we are back to confusion :) First off Marcus! quit tickleing around and help out here!! :debil:

Terry lets try this senario, one fork with a bladder and one without, both forks without the RB washers. Set the oil level on both forks at 100mm. The air spring that is created inside the fork by compression, are you telling me that both forks will compress equally with the same force??
 

marcusgunby

LIFETIME SPONSOR
Jan 9, 2000
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Steve wont the air spring really be the same(assuming airgaps are adjusted accordingly) but in 2 separate places??-its just got a divider, i believe its the RB that is the main problem, i remove both to make it like a std fork and so the airgap size etc is more like a conventional fork.

So with bladder and no RB i would set the airgap at 90-100mm.
With no bladder and no RB i goto 120-135mm.
 

terry hay

Member
Nov 8, 2003
200
0
Steve
The oil levels would be different in my scenario but the air quantity or volume would be the same. The volume of oil is not as important as the volume of air.
So lets say the material volume of the bladder was 40cc then one fork would have 40ml of extra oil to compensate for the other having the volume of the bladder. Then the compression should be identical
 

steve125

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Oct 19, 2000
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Ok after re-reading these posts a doing some research, I understand now that we both have got this figured out! Thanks for your time Terry! :thumb:
 
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Jeff Howe

Member
Apr 19, 2000
456
1
Terry,

If what you are talking about is a RT CV seal, I don't want one. If it's something better, with less rod stiction I'd be willing to look at it.
 

terry hay

Member
Nov 8, 2003
200
0
Shocknut
The RT CV seal is a waste of time in my opinion in 2000 and above models with the alloy damper rods. The replacement kit I'm talking about is a billet replica of the original, containing only a teflon coated shaft bushing. This not only removes the unwanted workings of the valve but also further reduces stiction by not having the seal in there either. The fork then functions the same as most other designs.
 

terry hay

Member
Nov 8, 2003
200
0
Steve
The bladder had a dual function in this design. First of all it had to accomodate the volume of oil being displaced by the damper rod on compression. Also it had to accomodate the volume of oil supposedly bypassing the cartridge sealband creating the low speed air effect. But now that we have negated this operation and have a flow path between the two areas, all areas are now subject to the same compressive forces of the fork under compression. Because the air trapped inside the bladder should react the same as the air above the oil Both your way and my way should function equally if the bladder material volume is compensated for. So I guess its a case of "Same horse, different jockey".
Best Regards
Terry
 

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