YZ 2002 KYB Midvalve

Jeremy Wilkey

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#1
Hey all Chad Newton From total control had the jump start this year on the 2002 models. We got to take a look at the new 2002 YZ forks. Here is the early report on the new "dual" piston midvalve.

The first image is of the compression side of the midvalve. The old part on left the new part on the right. The changes should acomplish a few things. By reducing the total flowable area the stack will be more sensetive to lower speeds. The fluid veolicty will be higher and the stack if float was reduced would ebcome more easily modulated.

Total deflection should decrease however the actualfeed port area has increased so velocity should be lower on high speeds. (this is good) We are getting more low speed control and less highspeed damping .. very cool.. Take on thing into consideration this is only from a quick overall perspective, deflections are rather large in a midvalve so the spefics become somewhat muddy, obvously real testing will provide a wealth of new information.
 

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Jeremy Wilkey

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#2
This is the rebound face of the new piston (on right). The area of the ports has remained farily constant with the large flats on the side however instead of four ports we now have two. The large pockets allow the fork to be light and responsive in feel yet not lose control over higher speeds and larger deflections.
 

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Jeremy Wilkey

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#3
This is the two part aspect. The peice on the right is the actual face of the piston (upsdide down) , the peice on the right channels the fluid, and serves as the valve body. The two parts work as one and I believe KYB made it two part in a effort to make production easier. It woiuld have been very difficult to produce the piston in one peice.

Kevin Stilwell made a simmliar designed (Two peice mated surface piston) in the early 90's but it techically had nothing in comom with this design.
 

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Jeremy Wilkey

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#5
The new midvalve and rebound somewhat mimics the Ohlins design used in thier forks. (its not the same) But there are simularties..

For the record I don't like the (ohlins 25mm cartrdige and honestly rudemetary fork (hydraulicly related) internanals) The 32mm KYB fork defiently has some intresting potential.


Regards,
Jer
 
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#8
Question for Jer:
Is it true that back in 2000 Yamaha asked Ross to come up with something that they could do to the forks so they could say someting other than BNG's?
Also, is it true that Gas Gas motorcycles actually have true "works" WP suspension, or at least superior to KTM's?
Regards
 

Jeremy Wilkey

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#9
While I don't actually know.. I doubt the marketing people would have gotten much rise out of Ross... I seriously think the new midvalve is ligit, and not just a marketing concept... As for the GAS GAS stuff.. Difrent but not superior..


Jer
 
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#10
Thanks for your reply.
Pretty cool you monitor and are so involved here.
I ride an 01 426 and just had the susp done by RT. It seems night and day better. Actually I didn't have many complaints about the rear but the front was horrific. Question: what do you know about the new CR 250 suspension and any comments. Pick mine up in the morning.
Thanks,

David
 

Jeremy Wilkey

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#11
Here is a photo of the Ohlins 25mm Piston that I spoke of earlier. As you can see the piston is design is atempting to maximize the area of flow, while producing a miniumum of velocity.
 

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JB

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#12
question jer. i had the suspension redone on my 01 and love it. should i swap it with my 02 suspension, or have the 02 redone??
 

Jeremy Wilkey

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#13
JB,
The 2002 is superior in potential as far as the forks are concearned. The Rear shock will not match up with the 2001 As it has a different Linkage ratio.

Regards,
Jer