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KYB 46mm Fork Differences and Stock Stack Specs 99-01 YZ

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Hi guys, I've also posted in suspension section. But I'll try here also.

Its for my 99 yz 125/ HP 144 build.

I'm trying to gather some information about what valve stack arrangements about this model. Before I cut loose and open the forks and shock up.

Specs on Both mid and cylinder/base on the 46mm KYB open chamber forks and the stack arrangement is on the rear shock.

And any problems/areas what can be addressed to make these old forks work well.

So far I've read that the rods changed from steel to alloy between 99 and 01.

And apparently the 99 does NOT have the cylinder valve. So far I can only get 01 stock valve stack specs.

So far I have springs for my weight, .43 front (.41 stock) 4.8 rear (4.6 stock). The forks I've replaced the outer bush, new seals and new bottom bumpstops, the rest is un-touched and stock.

The shock. Fresh oil and gas. When it comes to opening that up again. I'll replace the seal head and bush when I come to re-vlaving it.

Thanks for your help guys.

Edited by Street_Kleaver

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The stokc valving is terrible...awful. ANYTHING you use will be an improvement.

You can find specifics in the suspension forum. As far as feel and performance, they can be made to work really, really well.

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The CV forks started in 1998. Also if there is a bumper in the fork than it has a CV.If the valving is similiar to the 250 than it is going to be a little harsh on small square edge stuff. To much high speed compression. They can be improved pretty simply with the right shim changes.

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Thanks so much guys. I got 2001 125 specs so far. I'll work off that as a base. I have a stack recommendation to add onto the 01 specs I'll try that out once I've ridden the bike.

Keep you all updated on my progress!!

Cheers

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I believe the 98-03 forks were the same except for a few parts being made from aluminum that were brass. Looking back, it was a very slow time period for yz forks.

I still think one of the best forks I ever used was a set of 01's that I revalved myself.

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Cool thanks Rcannon. I have the stock stack arrangements for the 01. I'll use that as a base with some minor changes to the base and mid that have been suggested to me.

Keep you all posted of the outcome when I get there.

Thanks again guys

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Finally, Curiosity got the best of me. Got it all apart safe and sound. Was easier than I thought!

It has steel rods. Bit of rust on there. Also some scoring, only small like a vice scratch, can just feel with your finger nail. The cylinder valve seems a bit loose on the rod. Is that a problem? I know the seals can leak being a issue.

Anyway here is my fork specs.

99 yz 125 46mm kyb OC forks.

Base valve.

25 x .40

Piston

24 x .10 (7)

24 x .10

14 x .10

22 x .10

12 x .10

20 x .10

18 x .10 (seized on shaft, got bent getting it off )

16 x .10

14 x .10

12 x .10

18 x .50

Rebound

11 x .20 (3)

14 x .10

16 x .10

18 x .10

20 x .15

12 x .15

27 x .10 (4)

Mid Valve

27 x .10 (4)

20 x .10

16 x .10

14 x .25 (2)

25 x .40

11 x .30 Below spring collar.

After all this, the only thing my 99 shares with the 01 is the mid valve stack.

Thanks guys.

I've got a recommendation for a shim stack. Trying to chase up a cylinder valve replacement.

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