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KTM Cone Midvalve Valve?


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Pay no attention to the man behind the curtain...or was it Dorothy, we're not in Kansas anymore.

Honestly this stuff gives new life to old ideas. I have not used or played with the cone valve, so it may be all that. I suspect this is merely one piece of the puzzle with the MXGP team they mention in the info.

I have seen this utilized before, just don't recall where.

PK

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I wanted to wait till I have some more time on the forks, but at least I've got some pics. I think the concept is great and the first rides really surprised me on how well the cone valve is working. Very smooth feeling regardless of what you hit at all speeds. As usually WP looses a lot with detailing and quality, but overall I think they have a winner here. Cone Valve angle is 15ยฐ, CV spring is 25N, stock (crappy I may add, pistons in the pics are modified and ported) WP/KTM 23mm pistons on MV AND BV. BV has a small 30mm ICS piston with a 8.9N spring.

They use a bleed-less MV piston with a bleed shim on the rebound to compensate. Not a good idea IMO and I've already converted to a more standard setup. You can either set a preload or float on the CV using shims am I'm running a setup with a very small float (09 250XC). Naturally very light valving with the small BV piston.

Something apart from the CV I really like on those forks is the seperate dust seal/seal carrier which you just unscrew from the fork legs. No more ruining the bushings or hammering the fork legs apart - just unscrew and everything comes out easily. Well, at this price there ought to be something :usa:

One more thing, I don't see a reason those parts (CV) can not be retro-fitted to existing fork with 12mm rods. Only concern is rod length as the CV-assembly is longer than a std. piston/shim setup.

Bushmechanic should love this setup, as it greatly reduces the risk of cavitation on the MV since the flow path is much smoother than over the edge of a shim stack ๐Ÿ‘

K800_CV1.JPG

K800_CV2.JPG

K800_CV3.JPG

K800_CV4.JPG

K800_CV5.JPG

Michael

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They use a bleed-less MV piston with a bleed shim on the rebound to compensate. Not a good idea IMO and I've already converted to a more standard setup. You can either set a preload or float on the CV using shims am I'm running a setup with a very small float (09 250XC). Naturally very light valving with the small BV piston.

๐Ÿ‘

Michael

Excellent pics, thanks.

What don't you like about the bleedless midvalve, and the rebound bleed shim you are referring to , how is it set up in the rebound stack, right against the valve face or a smaller crossover?

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Now I remember, an outflow valve for aircraft use a similar design but controlled differently.

The taper angle is critical.

When I penned something similar years ago, I decided the best setup, though I did not build or test it would not use a coil spring.

The best setup I believe is to use disc spring or belleville washers. This will allow you to tune seat pressure, peak pressure, and depending upon how they are stacked and what thickness the amount of progression not only for displacement but force along the displacement curve.

Michael, did that reduce the overall travel but the added length?

PK

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What don't you like about the bleedless midvalve, and the rebound bleed shim you are referring to , how is it set up in the rebound stack, right against the valve face or a smaller crossover?

I see a bleed shim as a shim that sits against the piston face and does not cover the ports completely. On this particular fork (setup for a 250SXF, 0.44 springs) it was a single 16x.1 . I do feel that while you want some additional free bleed on the MV piston a shim with 0.1 thickness is too much. This is about 3 times more area than a 1.2mm bleed hole. I'm pretty conservative on my rebound setups - tapered two stage stack with bleed hole in the piston, traditional japanese style ๐Ÿ‘

Michael, did that reduce the overall travel but the added length?

No, the length of the complete rod/piston assembly is similar between different forks. While the rod is shorter on the CV forks they compensated with shorter top-out springs. The whole CV fork is longer though as the std. WP/KTM forks as they needed more room for the ICS assembly in comparison to the bladder ones.

CV6.JPG

Michael

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thanks for the great pictures Micheal, the female bit of the cone valve was where I got stuck :usa:

this thing works well but yes its still got shims ๐Ÿ‘

http://www.husaberg.org/index.php?set_albumName=bushmechanic&id=blowoffs_008&name=gallery&include=view_photo.php

CV forks ! theres an acronym everyone thought was long dead

servus

Bushie

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I really like on those forks is the seperate dust seal/seal carrier which you just unscrew from the fork legs.

yes, that's a bummer ๐Ÿ‘

So what do you guys think about this modded midvalve? It looks to be along the same principles, w/ PMK's belleville idea.

Nost ?

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its all about variable holes and port growth in area vs pressure, shims do a good job but have faults(shearing of the oil etc) so its just a case of is the cone a less compromised system, sounds to me like it works well with minimal tuning, maybe a good way to the future.

Even daves blow off design is still following the same pricipal really, but his is less linear than most, what i would love to be able to do, is to ride the best fork made that covers all bases(plush but firm etc etc) , put it on a dyno, then see if the cone fork can closely match it without reinventing the wheel and spending millions of hours tuning it, if so we have the winner.....๐Ÿ‘

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MIchael , that's some NICE parts! ๐Ÿ‘:usa:

So what do you guys think about this modded midvalve? It looks to be along the same principles, w/ PMK's belleville idea.

midvalve.jpg

This was modded to my WP4860 many yrs ago.:D๐Ÿคฃ

hey Jed,

I used the belleville washer type a few years back but had a issue with cycling. They didn't hold up. Did you have this issue?

Michael, Once again you come through... Thanks๐Ÿคฃ

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So they have ditched the bladder. Or has it even ever been on the Works forks?

I don't think the works forks ever had a bladder - this is a result of the preload adjuster as it takes away precious space in that area. I like the bladder and I would happily give the preload ajuster away for it.

the news are no more bladder, even on oem from 2010

Yeah, toghether with a linkage, Trellis frame and Husaberg engine ๐Ÿ‘

Michael

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Micheal with the ICS spring/piston instead of a bladder; do they (WP) still use a pressure relief valve to dump excess oil or is it a postion related bleed hole like the jap stuff ?

read somewhere once that Terry Hay was putting tapers on the KYB BV "stem" to bleed off excess oil from around the ID of the ICS piston rather than relying on the OD bleed.

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  • Bryan II changed the title to KTM Cone Midvalve Valve?

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