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Convert WP Closed Chamber Bladder Forks to a KYB/Showa style Spring ICS internal cartridge - WP Race Performance Fork Kit (Collective Tuning)

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Yes apart from on pre 09 forks as those were too stiff in materials

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There are two problems with the bladder. The biggest one is the bladder puts a lot of pressure against the oil from the offset. You can feel this when you build a WP cartridge and notice how it extends all the way and slams to the end after cycling it. Build a Showa or KYB cartridge and the push rod generally won't extend to the end of the stroke all the way with the stock IFP springs. The cartridge is so much more plush at the first part of the stroke, it takes little to no energy to push the cartridge through the initial part of the stroke. It stiffen's up very quickly, but it's all about that initial hit which is part of the problem with WP's bladder design.

The second problem with the bladder comes from the blow-off system. They use a stupid spring and o ring, which is absolutely nonsensical and doesn't work. Just pump a WP cartridge a few times after building, sometimes when you pump it, a bunch of oil comes out, other times nothing happens. So I can't imagine what it does at high speed, probably releasing on some hits and not on others. The spring based IFP blow-off system releases pressure/oil from the inner cartridge through a bleed hole on the side. It's a simple and elegant way to deal with this problem and every time, it blows off exactly the right amount to prevent too much pressure built-up. I believe the bladder forks build up too much internal pressure, which is why they work well in the morning, but by afternoon they're harsh as shit.

Having experienced Öhlins and done a lot of tuning with their high pressure IFP system which works more like a shock then a fork, it has the same low-speed initial harshness problems the bladder forks have. Mostly because there is so much damn pressure behind the oil. I've done tests lowering the IFP pressure, but unfortunately the fork is designed to work with high pressure and it cavities very easily, unlike the Showa/KYB design.

So all in all, I do believe the spring IFP will solve MANY of the issues with WP forks. Running lower outer cartridge oil and a more constrictive perch will solve the mid stroke harshness and bottom issues in one modification. So you'll have a plush fork at the beginning of the stroke and a very well balanced fork mid stroke with excellent bottom characteristics without resorting to an expensive bottoming cone which none of the Showa/KYB forks have.

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So all in all, I do believe the spring IFP will solve MANY of the issues with WP forks. Running lower outer cartridge oil and a more constrictive perch will solve the mid stroke harshness and bottom issues in one modification. So you'll have a plush fork at the beginning of the stroke and a very well balanced fork mid stroke with excellent bottom characteristics without resorting to an expensive bottoming cone which none of the Showa/KYB forks have.

 

Nice detailed explanation. What are your plans, do you intend to try the WP Performace Kit?

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Thanks for putting in so much effort to experiment and share your results. I'm looking forward to see how this turns out. I'm really curious how your friend's 350 turns out. What sort of riding do you and he do?

Edited by SeanM327

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Tye you say without resorting to a expensive bottoming system but none of the mods listed are anything like cheap ?you could buy complete new modded sss carts for less than some of these mods

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Thanks for putting in so much effort to experiment and share your results. I'm looking forward to see how this turns out. I'm really curious how your friend's 350 turns out. What sort of riding do you and he do?

 

After 3 years dealing with properly sprung all stock components with little interest in sending my forks to a tuner (I prefer to learn and tinker myself), I felt it's the right circumstance to jump off the cliff first.

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Mini Ride Update: My buddy took his first ride this past Sunday and I'm hoping he will add his commentary. From what he explained to me, the forks were much more planted when going through whoops and did not exhibit any of the "pogo stick" effect he has experienced in the past. Unfortunately the track was mostly groomed and he was only able to give feedback mostly from the whoops section.

 

I suspect he needs more "rough" track time to report his feedback. Also, since he had both his fork and shock re-valved along with the kit, he probably won't be able to convey what impact the WP Performance Kit has versus the re-valving.

Edited by tk2stroke

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Tye you say without resorting to a expensive bottoming system but none of the mods listed are anything like cheap ?you could buy complete new modded sss carts for less than some of these mods

Ohh you're absolutely unequivocally correct. The smart thing is to ditch 'em.

However, for me it's more about experimenting and understanding, rather then simply making them work. If I truly, really wanted my bike to work perfect forever, never to touch it again, I'd own a Japanese bike. For me, I love tinkering and learning. Modifying the stock components in some slight way's to make it better is more fun. Putting japanese bits into my Austrian forks, simply doesn't interest me. Plus WP makes the upgrade components because they know it's a problem.

Is it a more expensive route? Yes… absolutely! Sometimes it's worth while going the expensive route to keep the bike somewhat uniform and to learn.

Mind you, I won't be doing anything for a while because I'm broke, but the IFP kits are on my want list. :)

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Well so far the owner thinks they are a bit better in whoops and that's after a revalve on the mid at the same time ,don't hold your breath

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Well so far the owner thinks they are a bit better in whoops and that's after a revalve on the mid at the same time ,don't hold your breath

 

"A bit better" is not what he conveyed. After one ride has confirmed that the "pogo stick" as he called the deflection is entirely remedied after his experience in whoops/rollers. He is exceptionally pleased after one ride but wants more time on a rough track before he shares his thoughts. 

Edited by tk2stroke

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And as you said it was revalved so it's a little hard to use as a baseline of better or worse

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I dont know the actual kit that is discussed here (as most of us I assume), however, as it seems it the same design as the CV unit.

If this is true, it also have excessive preload on the spring, so no real "advantage" or to put it better "preload tuning possibilties" on that one...

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I dont know the actual kit that is discussed here (as most of us I assume), however, as it seems it the same design as the CV unit.

If this is true, it also have excessive preload on the spring, so no real "advantage" or to put it better "preload tuning possibilties" on that one...

 

Yes, they seemingly are the same design without the CV, though to my knowledge (I haven't seen the install instructions) the WP Race Performance Kit is simply installed and then bled out.

 

How do the CV forks achieve the preload on the spring?

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I dont know the actual kit that is discussed here (as most of us I assume), however, as it seems it the same design as the CV unit.

If this is true, it also have excessive preload on the spring, so no real "advantage" or to put it better "preload tuning possibilties" on that one...

 

Exactly, but hey some people dont listen.

The CV unit no doubt is preloaded to help reduce cavitation in the cone mid setup and to add  some additional digressive dampening to the fork in the absence of very little or zero preload recommended on the main springs?

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Kit Arrived: Yesterday was a good UPS day as I received my WP Race Performace Kit (WP-RPK). The first thing I noticed (on my friends kit as well) is that WP screwed the pooch on the color choice. The burgundy red doesn't match any color scheme for a KTM and it's just an odd choice or poor execution. Nonetheless, the color is not why I paid $1k for the kit...but it is odd that it doesn't match the marketing images.

 

Kit Teardown:With not having the tools I need to install the kit on my 250sx here in Utah, I'll have to wait 2 weeks until I take a trip back to my home in South Carolina. With the extra time, I decided to tear down a kit with the intent to measure the stock shim stack for future reference. I'll need to grab a good set of calipers before I can record the stack settings.

 

For those of you with experience, maybe you'll be able to comment on what you see in the photos.

 

16184201523_190f1f04d5_z.jpg

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Base valve has a lot more flow then the stocker.

So you're telling me it DOESN'T come with the cap tool? How the F do you build the fork without the cap tool?

Edited by tye1138

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Base valve has a lot more flow then the stocker.

So you're telling me it DOESN'T come with the cap tool? How the F do you build the fork without the cap tool?

 

Nope, no tool. Had to hack my sag scale into a multi-function suspension tool.

 

What do you make of the smaller shim in the middle of the stack, what's the general purpose of that?

 

16597497187_e5416de084_z.jpg

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It's called a cross over shim ,you will have no idea if it's the piston design ,the shim stack or the ics that makes it perform differently

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Ooops.

Looks not good to me.

You cant get enought torque with the sag scale and the srews...

Sorry.

I have a very cheap tool for this, but i dont know the correct name in englisch.

Try the google picture search with

"stiftschlüssel"

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Ooops.

Looks not good to me.

You cant get enought torque with the sag scale and the srews...

Sorry.

I have a very cheap tool for this, but i dont know the correct name in englisch.

Try the google picture search with

"stiftschlüssel"

The correct tool would be called a "Pin Spanning Wrench", but my hack worked as the cap is not torqued tightly

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