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KYB Bladder Forks
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Posted by: terry hay---------------------

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

Posted by: steve125---------------------

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!

Posted by: terry hay---------------------

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

Posted by: Rcannon---------------------

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

Posted by: marcusgunby---------------------

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.

Posted by: terry hay---------------------

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

Posted by: marcusgunby---------------------

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

Posted by: steve125---------------------

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.

Posted by: terry hay---------------------

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?

Posted by: steve125---------------------

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!

Posted by: terry hay---------------------

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

Posted by: Jeff Howe---------------------

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.

Posted by: terry hay---------------------

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

Posted by: steve125---------------------

Quote:

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:

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. Cool!
Catch you later
Terry

Posted by: terry hay---------------------

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

Posted by: dbrace---------------------

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.

Posted by: marcusgunby---------------------

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

 

Posted by: steve125---------------------

Quote:

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!!

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??

Posted by: marcusgunby---------------------

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.

Posted by: terry hay---------------------

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

Posted by: steve125---------------------

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:

Posted by: Jeff Howe---------------------

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.

Posted by: terry hay---------------------

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.

Posted by: terry hay---------------------

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

Posted by: steve125---------------------

Thanks Terry! If you noticed 10 minutes before your last post, I edited my previous post.

Posted by: Jeff Howe---------------------

Might as well pull them out and round file them and save that little bit of weight is the way I looked at it. They are perfectly fit for the trash can.

Posted by: know_fear---------------------

Now that everyone is happy, here's a question for you. I removed the conventional forks from my KDX 220 because of the underhang and the imprecise steering (due to fork flex). I put on Kayabas from a 2000 KX125. I believe these used forks are totally stock but I rebuilt them and put in 500cc of 5 weight per leg. They're far superior to the KDX forks especially on an MX track but in the woods they leave a lot of room for improvement.
I'm 180 lbs and not a fast rider but we often find ourselves riding in creekbeds and over some nasty terrain that some would call a Trials course. The springs are .40 Kg/mm by my measurements and eventhough the KDX is heavier than a 125, I feel that things need to be softened considerably. These are the bladder style forks but I'm not sure where to start. I'm new to susp. tuning but willing to try improving things on my own (with help from this forum).
So, first, does 500cc of 5 weight sound right? Can these springs be retained by improving things with valving changes?
When giving advice, it'll probably be best to explain things as if you're talking to a six year old!

Posted by: terry hay---------------------

Know Fear
For the type of riding you are doing the springs should be fine, but as you can gather from the content of this post there are a few issues internally. Firstly as a newcomer to the suspension game I would suggest we keep it simple. Firstly remove the bladder (Go Steve!) and the white sealing band from the cartridge. There is also a finely machined washer on the flange at the top of the cartridge where the spring seats. This inhibits oil flow to the lower portion of the fork. With the sealing band removed there is possibly no reason to touch this, but I remove it to ensure maximum flow and replace it with a normal spring preload washer that doesn't seal the area. I wouldn't recommend sitting the spring directly on the flange itself. If you don't have a preload washer you can drill a few holes in the machined one. Just make sure you leave no burrs. Run the oil level at 120mm from the top with the springs out and the fork completely compressed. The midvalve on that particular model has one of the worst production designs I have come across. In fact the 2000 KX fork should have seen Mr KAYABA and his team of designers firmly attached to the testicle clamp. You really need to address the midvalve and base valve to get the best out of this model for your application. Now that we have addressed the design issues I'm going to stop short of any valving recommendations as this conflicts with a lot of the guys on this forum. After all thats how they make their living.
Regards
Terry Hay

Posted by: know_fear---------------------

Okay I'll give that a shot. I doubt that I'll be able to get that done and give it a test ride this weekend but I'll let you know. We're starting to get a lot of snow here so the lower trails are still open but getting really muddy.
How about oil weight, should I stay with 5?

Posted by: marcusgunby---------------------

With that std midvalve 2.5wt wont do any harm IMO.

Posted by: Jeff Howe---------------------

I've not ridden a 00 KX 125, but a friend still has a 01 KX 125 with stock suspension and those forks are hands down the worst stock forks I have ever ridden on a MX track. They are so harsh it blows my mind, and that shock is equally as bad. So Terry, Mr KYB should not have been released from the testicle clamp for another full year there.

Posted by: marcusgunby---------------------

Jeff you should try a 01 KTM 125sx-that makes the kx fork feel way plush LOL.

Posted by: Jeremy Wilkey---------------------

Well for one I actually agree with all of you on the bladder fork! I must admit I was a die hard who was shown the error of my ways.. But it took some hard lessons first.. Jeff was a principal in that change, our debates are always productive, and spirited.. (I hope you butt chewing comment was in good humor Jeff, I be bummed if you ever thought that your opinion was not welcomed hear by me. I consider you a good friend and I hope you know that!)

As for the bumpers..

I think maybe you guys are missing something on these new forks.. These are not bladder forks as much as they are "Semi sealed forks".. That check valve is there to prevent any low pressures.. I don't interoperate these forks to function the same.. KYB is actually building a pressure in the forks cartridge that will slowly leak out, this enables the fluid pressure to rise without fork travel and solve many of the open Cartridge inconsistency issues. So its not a restrictive barrier issue.. Set the oil level lower and you won't have any harshness but you will get more solid and consistently working fork..

BR,
Jer

Posted by: Onore GT---------------------

[QUOTE]Originally posted by terry hay
Steve
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? [/QUOTE

The 2004 KX fork does have a bladder but the purpose of the bladder is significantly different than the old model bladder fork. With the check valve or restrictive barrier now freely allowing oil into the lower portion of the fork and holding pressure in the lower portion of the fork, the fork is less prone to cavitation. Although pressure within the cartridge is still changing as the fork goes through it's stroke, the cartridge is effectively sealed from the drastic change in pressure of the airspring as the fork moves through it's travel.

Thus, with the lower portion of the fork effectively sealed and "charged," the role the bladder is to take up the volume of oil displaced by the piston rod rather than only being used to manipulate the size of the air chamber. There is still some effect of a speed sensitive airspring in the new fork but to much less of a degree than the old bladder fork because the lower portion of the fork is already charged and the bladder is under pressure.

If you think of the fork in these terms, effectively this is a sealed cartridge fork. The top of the cartridge is not absolutely sealed but that is not necessarily a bad thing bercause air can escape from the cartridge and the cartridge is continuously charged every time the fork moves through it's travel to maintain pressure within the cartridge. The oil volume is also much greater than a true closed cartridge fork also. This system is not necessarily better than a sealed cartridge fork, I just don't think we are ready to throw the baby out with the bathwater yet...

Posted by: terry hay---------------------

Onore GT
The designer of the bladder fork obviously had his own agenda when he first ventured into this design folly. Wether he wanted a poorly designed speed sensitive air spring or a poorly designed dual chamber fork is not important. The fact that the design reeks of failure, is. When such dramatic improvements can be so easily effected by removing the offending items and reverting back to normallity it lays waste to any good intention the designer might have had. Once again I am disappointed that a concept is released in an underdeveloped state, and we, the motorcycle buying public are asked to be patient while they get it right.
Terry

Posted by: steve125---------------------

Quote:

Originally posted by terry hay
Onore GT 
Once again I am disappointed that a concept is released in an underdeveloped state, and we, the motorcycle buying public are asked to be patient while they get it right.
Terry

Yep! like waiting for over 10 years and the CR125 motor is still slow. So Honda threw in some bladder forks just for fun. :confused:  

Posted by: bclapham---------------------

yes steve, but if they put a decent motor in it, what would you have to do in an evening?:confused:

Posted by: Onore GT---------------------

Quote:

Originally posted by terry hay
Onore GT
The designer of the bladder fork obviously had his own agenda when he first ventured into this design folly. Wether he wanted a poorly designed speed sensitive air spring or a poorly designed dual chamber fork is not important. The fact that the design reeks of failure, is.
Terry

Don't you think you are overstating your case a little Terry? I think they could have efffed it up a lot easier than designing an entirely new system. When was the last time you set out to design and execute something poorly?

No but really, I see your point and agree. The fact is that most of this stuff that shows up in production is handed down from factory bikes. Why doesn't it fly for production? The factory forks were made with higher quality components and manufacturing processes? The forks have to be tuned too specifically for each track or terrain? What factory rider desires something that is completely out of the realm of what a normal person desires? It is all these things and many more. Because it did not work well in it's first production version is that reason to completely scrap the idea and start on something else? Personally I am not ready to toss out the latest version. The 04 fork has some pretty cool features and for the most part people seem pretty happy with the fork here. Obviously I cant speak for your side of the world and your customers may have a completely different opinion, however.

Posted by: terry hay---------------------

Onore GT
Perhaps your right and I am overstating a little. The fact remains that the system is a step backwards from previous models. I'm sure there are many customers out there who are happy with their bikes, complete with bladders. (This doesn't mean they wouldn't be happier without them.)
But, when presented with the task of improving the fork for those who are not, the solution is obvious. This in turn begs the question,"What were they thinking when they produced this?" I would doubt very much that we would find a bladder in a well tuned factory fork.
Terry

Posted by: Onore GT---------------------

Terry, Point taken, and I guess that is the question of the ages isn't it, "What were they thinking?" Unfortunately there are a lot of steps that happen between design and final execution and lots of places to make mistakes in between. Sometimes problems with the end product are a result of separation of the engineer from the end product, sometimes it is incomplete testing, sometimes it is poor feedback from the testing staff, sometimes it is a misinterpretation by test riders about what the general public will want, and sometimes it is a mistake in production. And then there are all the other considerations about the chassis and engine setup during testing, was the system selected to improve handling with a sacrifice in suspension feeling? As we all know the final production or race setup is a combination of sacrifices to create an acceptable overall package for the rider.

Just curious, have you guys worked much with the new KX fork? Overall what are people's opinion of the new KX fork? Of course you hear people griping about the suspension everywhere but so far in the states I think once people get some time on the bike and get it set up with proper springs when necessary I think people are pretty happy.

Quote:

Originally posted by terry hay

I would doubt very much that we would find a bladder in a well tuned factory fork.
Terry

Of course production bikes are always a couple to a few years behind what they are using on the factory bikes but you might be surprised by who and when the bladder forks have been used…

Posted by: marcusgunby---------------------

My comment would be, i think the Kayaba guys were a bit stuck on how to goto the next level, the TC is IMO the way forward , but patents stop them copying that design, the basic KYB fork was not much different from 95 onwards(when we got the midvalve) since then weve had bumpers and cones(nothing radical IMO)and CVs(IMO mainly designed for the big catridge YZ fork) and now since 2000? the bladder, im still grappling with how it actually improves the fork action in the designers eyes. I know when riding they are not good forks, and they feel good when modded(ie made more conventional)
SO i guess the answer isnt performance, but having a reason to employ R&D staff?

So whats going to be the next big thing?? how are they going to make the next leap?

Posted by: steve125---------------------

Bell-bottom upper fork tubes Marcus? :confused: The latest Factory KYB's are huge for 04!

Posted by: terry hay---------------------

Onore GT
How dare you employ the voice of reason just when I was getting passionate!
Now I have to climb down from that soap box and start again.
The KXs have been on a downward spiral (saleswise) in this country until the arrival of the KXF250. Since its arrival I have worked on 6 KXFs and I have an RMZ booked in on Monday. I believe they are the same but I'll let you know if there is any difference. Every one is complaining of similar things with the forks. Harsh, deflecting, armpump. Mind you I have to be fair and say that the only time I hear from people is when they're unhappy with their bikes. We had Team Kawasaki out here on Monday testing on our supercross track and overrunning our workshop. Interestingly they also disable the bladder arrangement. We recently set up a bike for Dirt Action magazine in which we left the bladders intact. It was raining that day and we couldn't test sufficiently. We are due to do some more development with them on Saturday. You seem rather passionate about the bladder arrangement yourself. If you have any suggestions now would be the perfect time to speak up as I am always willing to test and the mags are always keen on a new angle.
Regards
Terry

Posted by: Steve47---------------------

Alright guys,

I know nothing about forks and don't understand how they work! That's why I have my friend Shockdoc helping me out tuning them. The thing I know is how they feel!!

The other thing I know is that I owned every KX250 since 2000 and my 2004 has the worst forks of all. Terry described it perfectly "Harsh, deflecting, armpump" Braking bumps is a nightmare for me right now and my arms are done after 5 hard laps. Not cool!

Yesterday, after reading this thread, Shockdoc disabled the bladder to see the improvement. Now I dnd't get much track time cause it at the end of the night and something went wrong with my shock rebound but I can tell you that the forks are tons better now. I can't wait to go back out and pound some laps.

Posted by: Onore GT---------------------

Here is your chance to knock me off my soapbox Terry...

I started using the subtanks back in 01 and have been using them ever since. On the 01 and 02 KXs I removed the internal bladders and just ran the subtanks. The 04 I am again running the subtanks but have left the internal bladders functional. I ride all of the local tracks here in southern California where the manufacturers are doing their production testing so usually I don't have to change much other than the addition of the subtanks, springs, and some additional low speed compression to make the suspension work for me. And with the addition of the subtanks it seems there is a lot less tuning necessary, especially the subtanks with the adjustable restriction. Once you find a setting you can go from track to track with few changes. I can't begin to describe how well the subtanks work, never will I own a bike without them. I know that it is not possible to deliver a magazine bike with the subtanks on it, but after installing the subtanks I don't have to do much more to make the forks work really well for myself.

Jumping off my soapbox for a moment, the other thing that I fail to take into consideration often is that I am fairly tall and strong, and have a lot of leverage to work with that some people don't. I can see where lighter riders would think the forks are horrible as delivered.

Steve, I am curious to see how your test goes, let us know the results…

Posted by: NO HAND---------------------

Quote:

Originally posted by Onore GT
...I can't begin to describe how well the subtanks work, never will I own a bike without them...

What brand of subtank are you using? Is it true that oil will accumulate into the tanks?

Posted by: Jeremy Wilkey---------------------

Ongore GT,
I really appreciate your position.. Thanks for taking this down the trail..

As for the subtanks, I would not ride without them either..

As for the oil accumulation this is a small price to pay for condensation...That occurs as the oil vapor condenences after passing across the restrictive barrier..

Terry, here is an idea to try, leave the bladder in and set your oil level conservativly low and you'll have a fork that is more consistent and solid.. With in theory a slightly stiffer overall spring rate..

BR,
Jer

Posted by: terry hay---------------------

Onore GT
How can you defend a design parameter and then exceed those parameters by adding subtanks? Which, given that the bladder was originally designed to replicate the effect of the subtanks, aren't you simply admitting its failure by adding them in the first place?

Jeremy
I prefer to run slightly fimer valving and lower oil levels as a rule. It gives a more consistant action and often brings the comment "The harder I hit things the better it feels!" Exactly what we're after when trying to entice racers to go a bit quicker

Posted by: darnjr---------------------

Suspension experts,
What suggestions would you make for the 2002 model forks with bladders? I race cross country as an intermediate and if it weren't for conditioning, my forks would beat me to death. I had the forks and shock revalved after riding a friends 2000 KX that seemed to float over rocks and chop. I had a local shop do a "two-stage" valving job but I have never really been very happy. The low speed is fine, the shock is fine, but the forks are still harsh in the high speed choppy stuff. If I remove the bladders and seals, would the previous suggestions of lowered oil level still hold true? And would further valving adjustments be recommended beyond what has already been done?
Thanks for all the great info,
DA

Posted by: marcusgunby---------------------

Take out the rb and ride it with the same oil height, if its not good just put the rb back into place.I think you may need to get them valved again if they are that bad, ive found removing the rb helps alot but it doesnt make a terrible fork great.

Posted by: russ17---------------------

Quote:

Originally Posted by terry hay

Onore GT
How dare you employ the voice of reason just when I was getting passionate!
Now I have to climb down from that soap box and start again.
The KXs have been on a downward spiral (saleswise) in this country until the arrival of the KXF250. Since its arrival I have worked on 6 KXFs and I have an RMZ booked in on Monday. I believe they are the same but I'll let you know if there is any difference. Every one is complaining of similar things with the forks. Harsh, deflecting, armpump. Mind you I have to be fair and say that the only time I hear from people is when they're unhappy with their bikes. We had Team Kawasaki out here on Monday testing on our supercross track and overrunning our workshop. Interestingly they also disable the bladder arrangement. We recently set up a bike for Dirt Action magazine in which we left the bladders intact. It was raining that day and we couldn't test sufficiently. We are due to do some more development with them on Saturday. You seem rather passionate about the bladder arrangement yourself. If you have any suggestions now would be the perfect time to speak up as I am always willing to test and the mags are always keen on a new angle.
Regards
Terry

Terry,
How did the test go for Dirt Action in which you left the bladders in place, compared to diabling the bladder system as as whole.
The weather here has been terrible to test. and was curious in your findings.

Russ

Posted by: terry hay---------------------

Russ
We made several alterations to the fork and all the while reductions in lap times were made. The most significant one to this thread was a single mod at the end of the day that involved removing the seal band at the top of the cartridge to negate the bladder effect. 2.6 second lap time reduction instantly. This bike was in the care of Shannon Warner, assistant editor of Dirt Action magazine and he was our test rider. Our track is just over 2 kilometers long and is usually a +2 minute lap time. The results should be published next month.
Terry

Posted by: russ17---------------------

Sounds like you had a productive day

Thanks
Russ

Posted by: terry hay---------------------

Another interesting point was that in order to bring under control the hopping from the rear end of that bike (KXF250) we found it necessary to revalve the compression adjuster. Problem solved.
Terry

Posted by: Onore GT---------------------

Quote:

Originally Posted by terry hay

Onore GT
How can you defend a design parameter and then exceed those parameters by adding subtanks? Which, given that the bladder was originally designed to replicate the effect of the subtanks, aren't you simply admitting its failure by adding them in the first place?

Do you want to wrestle with this one again Terry? I must apologize for the delay in my response, my wife and I now have a new little baby girl to keep us busy.

Since the secondary air chamber and bladder serve a different function in the new KX fork I don't think that I am admitting failure of the bladder at all. The subtanks will improve fork action on any KYB fork and as I mentioned before, once I tested them I have used them ever since on all my KXs. If we are talking about the original bladder fork, yes, I believe that the speed sensitive springing characteristic is better controlled pneumatically rather than hydraulically.

I am not trying to say the bladder fork is the Holy Grail, far from it. I just think that as tuners when we are faced with a problem sometimes we tend to fall into the same course of action too often. Of course we have to draw on our past experience to improve anything but occasionally it takes looking at something from a different perspective to tune it properly. If removing the bladder provides the desired results than case closed. I will keep running the bladders in my forks however…

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