KYB Plastic Base Valve Piece


14 replies to this topic
  • almostinvincible119

Posted December 14, 2009 - 02:50 PM

#1

I know this has been posted a while ago, but I cannot locate the thread so I am posting another question. Where can I purchase this part that has the red arrow on it. I know there used to be a guy on here who was a KYB distributor and he mentioned he could get one.

Another question, they seem to break often (from what I can remember being posted) and there was supposed to be some mod you could perform to keep them from breaking.

If you could answer or link me to the old thread, I would greatly appreciate it.

Posted Image

  • DPW

Posted December 14, 2009 - 03:01 PM

#2

mod>> http://www.smartperf.../YZMODASSEM.htm

http://www.thumperta...ad.php?t=644121
http://www.thumperta...ad.php?t=659129

  • grayracer513

Posted December 14, 2009 - 03:25 PM

#3

You can get the part, called a free piston, from SMART Performance, also.

  • almostinvincible119

Posted December 14, 2009 - 03:32 PM

#4

Thanks a ton guys

  • nickeenoo

Posted December 14, 2009 - 05:10 PM

#5

http://www.thumperta...ad.php?t=852678

Dave is also offering them in a metal version. Check the thread to find info.

Nate

  • DPW

Posted December 14, 2009 - 05:12 PM

#6

http://www.thumperta...ad.php?t=852678

Dave is also offering them in a metal version. Check the thread to find info.

Nate



thanks....didn't know that. I had to replace one a month ago too...

  • nickeenoo

Posted December 14, 2009 - 06:42 PM

#7

No problem. I thought it was a pretty swift idea myself.

Nate

Visit the ThumperTalk Store for the lowest prices on motorcycle / ATV parts and accessories - Guaranteed
  • almostinvincible119

Posted December 15, 2009 - 02:40 PM

#8

I read somewhere, maybe the SmartPerf. site or one of those threads listed above that the metal version doesn't allow expansion thus putting pressure on the inner chamber tube and bulging it....

Anyone else see the same thing?

  • grayracer513

Posted December 15, 2009 - 03:02 PM

#9

I read somewhere, maybe the SmartPerf. site or one of those threads listed above that the metal version doesn't allow expansion thus putting pressure on the inner chamber tube and bulging it....

Anyone else see the same thing?

I haven't heard that, but on the surface, it already sounds like BS.

  • almostinvincible119

Posted December 16, 2009 - 05:48 AM

#10

Just having read the discussion i should point out that Kayaba made some aluminum pistons that were in some factory forks. This solved the piston breaking problem.

That was until the forks needed to be serviced. Closer inspection revealed the top section of the inner chamber had bellowed out so much that it was touching the outer tube (!)

Could air pressure do that? Or does it take hydraulic displacement to get up those sorts of pressures. Aluminum piston was OK though, it survived, just wrecked a far more expensive part. The inner seal had leaked.


This was from a noob, but who knows? Maybe someone made something like Daves design but didn't make it an open design such as he has?

Also want to point out that the inner chamber walls are pretty thick.

Post #24 on http://www.thumperta...ad.php?t=659129

  • oldnbold

Posted December 16, 2009 - 06:46 AM

#11

I broke that part on 1 fork about a year ago (after a huge crash) and didn't know it. I was chasing settings for weeks trying to get something to work like it should before the crash.

Thank God that part was available.

  • grayracer513

Posted December 16, 2009 - 08:32 AM

#12

That's an old discussion, but note that there is no indication as to whether the aluminum pistons the poster mentioned were vented between the upper and lower seal, as the ones Dave was offering are. Since KYB does not vent their plastic pistons in this manner, I would have to guess with some certainty that they were not. Then note that he stated that the inner seal had leaked. That would mean that oil from the cartridge had been pushed up into the top of the free piston, which would increase the pressure at the top of the chamber to the point where it would have caused the damage referred to at full compression. When this occurs with a plastic piston, it simply breaks it.

The reason the free piston is vented is twofold, and one of them is to prevent oil that may gather on top of the piston from hydro-locking the cartridge assembly by giving the oil a route out of the air chamber to the outer well of the fork. The other is to reduce the "air spring" influence on the inner chamber free piston, and allow cartridge pressure to be more completely regulated by the inner chamber spring(s) (ICS). With Dave's pistons opened up like this, I don't see a way for them to cause a problem of the kind discussed here.

Read:

http://www.smartperf.../YZMODASSEM.htm

http://www.thumperta...ad.php?t=650136

  • Wes Woodin

Posted December 17, 2009 - 03:58 AM

#13

Factory connection modify's this piece when they do a valving job on a set of KYB's. They told me that they have never had a set returned that they have modified.

  • DPW

Posted December 17, 2009 - 05:16 AM

#14

Factory connection modify's this piece when they do a valving job on a set of KYB's. They told me that they have never had a set returned that they have modified.


do you know what they modify? Is it something like this, http://www.smartperf.../YZMODASSEM.htm

  • Wes Woodin

Posted December 19, 2009 - 08:17 AM

#15

do you know what they modify? Is it something like this, http://www.smartperf.../YZMODASSEM.htm

Not sure, but they did tell me that it's proprietary.





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