KYB SSS fork problem


8 replies to this topic
  • KJ790

Posted June 20, 2010 - 07:15 PM

#1

I'm the first to admit, suspension is probably my least knowledgeable area on a bike. I can change fork seals and bushing, and turn clickers and what not, but I don't have any experience with valving. I recently bought a racetech gold valve kit for my 06 YZ450F. I followed the directions, everything seemed to go alright. However now I have a problem with the forks. When the wheel comes off the ground (going off of a jump, heading through whoops, or even pulling a wheelie), the forks seem to extend very rapidly until they reach the fully extended point, where they seem to stop violently with a clunk. It is so bad that when I go off of a jump the forks extend and when they hit the end it pulls the front of the bike down (almost pulls the bars out of my hands). It is like there is no rebound damping or something. I'm figuring I must have put something together wrong, but any insight into what I should look at before I pull them apart would be great. Thanks guys.

  • mog

Posted June 20, 2010 - 11:54 PM

#2

Sounds like a bleed problem , davej has a good guide on bleeding the tc fork

  • almostinvincible119

Posted June 21, 2010 - 03:46 AM

#3

I know this sounds crazy, but I've done it once. Make sure that small aluminum rod is back in the rebound piston...if its not in there. You wont have any type of rebound adjustment

  • KJ790

Posted June 21, 2010 - 07:51 AM

#4

Thanks guys. I know that the aluminum rods are in there, so that's not the problem. It could be a bleed problem, I followed the directions in the owner's manual, which I have heard aren't the best way to do it. I've never had a problem in the past with this, but it is definitely a good possibility. Any other ideas?

  • harrperf

Posted June 21, 2010 - 09:22 AM

#5

Overfill the cartidge..."force" the base valve in - must compress IC spring, then bleed by compressing full stroke.

I do it a simpler way...but it's hard to describe.

Are you sure you didn't remove the mid valve rebound shims?

They are on the top of the piston, or nut side.

  • Jeremy_Wilkey

Posted June 21, 2010 - 12:53 PM

#6

I think it is very important to not overfill the reservoir. If you do then the area behind the piston has a vacuum after the purge point. There are of course many opinions about what is happening inside the KYB TC forks, but I’ve found this to solve many problems all in one.

Setting the ht/volume per your manual, then leaving the o-ring just proud of the cap at the time of the final purge allows the pressure to equalize. Then you can seat the cap and not have a significant vacuum in the inner chamber after the cartridge purges. This promotes stability in the system. We added in testing a bleeder to the cap as the 2010 Showa CRF250 did in the production version. The above technique seems to overall work fine and not require and drilling and modification.

BR,

Jer

  • grayracer513

Posted June 21, 2010 - 03:25 PM

#7

Two things that come to mind here, one of which jumped up as soon as you said something about the manual. I know you well enough to think that you more than likely did not get caught in this one, but I'll float it out on the pond anyway. When you came to the part about the gap there was supposed to be between the damper rod lock nut and the rebound adjuster, you did end up tightening the nut against the adjuster, right?

http://www.thumperta...008#post8002008

OK, that out of the way, my guess is air in the inner cartridge, too. This, based on what I learned from DaveJ, is how I do it:

http://www.thumperta...14&postcount=39

  • KJ790

Posted June 21, 2010 - 06:07 PM

#8

Two things that come to mind here, one of which jumped up as soon as you said something about the manual. I know you well enough to think that you more than likely did not get caught in this one, but I'll float it out on the pond anyway. When you came to the part about the gap there was supposed to be between the damper rod lock nut and the rebound adjuster, you did end up tightening the nut against the adjuster, right?

http://www.thumperta...008#post8002008

OK, that out of the way, my guess is air in the inner cartridge, too. This, based on what I learned from DaveJ, is how I do it:

http://www.thumperta...14&postcount=39


Yes, I tightened the lock nut against the adjuster properly, I have seen where that has been confusing for people in the past. I guess I will have to try bleeding them differently and see if it fixes it (unless I see something obviously wrong when I take them apart of course). If it is air in the chamber then it seems odd that it has never happened to me before on any of my bikes when I would change the oil in the forks, and that this time it seems to be with both forks. This is what makes me think I screwed something up with the valving.

  • KJ790

Posted June 26, 2010 - 01:16 PM

#9

I figured it out, I'm just an idiot. I took them apart last night and found that I didn't have the total thickness of the midvalve right, so basically there was no rebound damping. I rode it today and it feels great. Lesson learned :)





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