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2002 yz250 2stroke SSS fork valving

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i ride a 2002 yz250 2T with 2007 yz250f forks. i got the forks used and did a rebuild on them when i first got them, been about 2 years with them now. I didn't even look at the valving when i first got them, just replaced all the bushings and seals with new oil. Now i am pushing the forks past their limits and decided to open them up and check spring rates and valving. (I have no idea how to set up shim stacks, which is why i am here).

i ride MX 30+C class and weigh 190 without gear.

So i did a home test on spring rates, first with 25lbs and again with 50lbs (just to double check the math). after converting to metric i found that they are .40 springs. Race Tech calculator recommends .44kg. so obviously these are to soft. (which i assumed from the beginning). Basically what i am experiencing, They are just to soft. Feel like i need to increase HS and LS compression damping. I am bottoming on flat landings from about 7ft up (small 3rd gear singles on the track) and braking bumps just blow through the first half of the stroke. Is what i am feeling mostly because the soft springs? should i get the correct springs first before touching the valving?

now to the shim stacks.

Base valve

Nut

spring cup

spring

32x.4

valve

32x.11 (x14)

25x.11

30x.13 (x2)

28x.12

26x.12

24x.12

22x.12

20x.12

18x.12 (x2)

16x.12 (x2)

15x.16

20x1.6 (x2)

12x.2

 

Mid Valve

Nut

washer

10x.26 (x2)

12x.12

14x.12

16x.12

18x.12

12x.12

20x.12 (x3)

Valve

20x.12 (x4)

17x.10 (x3)

11x.30 (x2)

17x.30 (x2)

spring

spring cup

 

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get heavier springs. pull the crossover out of the base valve.  start with lower oil level and work up to combat bottoming.

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get heavier springs. pull the crossover out of the base valve.  start with lower oil level and work up to combat bottoming.



Being I'm new to this i want to be sure.
By crossover shim, you're talking about the 25mm shim, correct? And should i completely remove it or put it against the spacers to keep shim height the same?

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Yes 25mm is the criss over, just remove it , but always get springs before playing with valving

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22 hours ago, cj_wai said:

get heavier springs. pull the crossover out of the base valve.  start with lower oil level and work up to combat bottoming.

Good advice by cj.  This is the route I take first after learning the basics of suspension about 15 yrs. back.  Once you have the correct springs for your weight you can ride it to determine what part of the valving needs to be addressed.  Of course this is once you've exhausted adjusting the clickers with the oem valving specs..   

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On 7/9/2017 at 0:43 PM, asian195 said:

Valve

20x.12 (x4)

17x.10 (x3)

11x.30 (x2)

17x.30 (x2)

Interesting mid comp stack, without much taper. On big hits I suppose those 17.10 shims will land on the 17.30, so the 17.10 will not permanently crease and deform. Normally those 3 x 17.10 shims would be a 14, 16 and 18 and on massive hits the outer edge of the 18 or the lower 20 bends down to land on the 17.3 cup shim.  You might be able to pull those face shims fully open with your fingers to see how it looks on full blow open.  Just for interest sake. I'm not proposing you change it yet.

Be sure to measure your mid comp float gap. Just stick two feeler gauges in between face and piston from both sides. Should be around 0.3mm.  It's a critical measurement in these (or any) forks impacting how quickly mid comp damping commences in the stroke and also how much ground chatter you feel in your bars. Like most things suspension it's a compromise setting matching personal rider preference.

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Interesting mid comp stack, without much taper. On big hits I suppose those 17.10 shims will land on the 17.30, so the 17.10 will not permanently crease and deform. Normally those 3 x 17.10 shims would be a 14, 16 and 18 and on massive hits the outer edge of the 18 or the lower 20 bends down to land on the 17.3 cup shim.  You might be able to pull those face shims fully open with your fingers to see how it looks on full blow open.  Just for interest sake. I'm not proposing you change it yet.
Be sure to measure your mid comp float gap. Just stick two feeler gauges in between face and piston from both sides. Should be around 0.3mm.  It's a critical measurement in these (or any) forks impacting how quickly mid comp damping commences in the stroke and also how much ground chatter you feel in your bars. Like most things suspension it's a compromise setting matching personal rider preference.



I've read a lot of the suspension threads and float always had me confused because i didn't know what it was.

So if I'm reading this correctly, float is the gap between the piston and first "sealing" shim? If yes, i guess i assumed the shims were tight to the piston.

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59 minutes ago, asian195 said:

 

 


I've read a lot of the suspension threads and float always had me confused because i didn't know what it was.

So if I'm reading this correctly, float is the gap between the piston and first "sealing" shim? If yes, i guess i assumed the shims were tight to the piston.

 

 

They are held against the piston by the spring. The float is the distance the shims lift before flexing. Its free movement no shim flex. Hope this helps. 

 

MM 

Edited by MartyMOOSE
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Think of float as "free lift" for your face shims. If you had none then your forks would feel super harsh.

 

 

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Another explanation of float is a 'delay' of dampening in which the forks can 'float' up/down over smaller obstacles without any deflection.

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2 things.

first, since we've been talking about float, how do you measure it?

On 7/10/2017 at 6:06 AM, numroe said:

Be sure to measure your mid comp float gap. Just stick two feeler gauges in between face and piston from both sides. Should be around 0.3mm.  It's a critical measurement in these (or any) forks impacting how quickly mid comp damping commences in the stroke and also how much ground chatter you feel in your bars. Like most things suspension it's a compromise setting matching personal rider preference.

i know numroe said this, but wouldn't that flex the shims? would measuring the gap between the last shim/spacer and spring cup be ideal?

 

Second, i got a set of .47 springs from a friend for free, so i installed those and rode with them yesterday. WOW, what a difference. They didn't dive through the stroke like they used to, which in turn let the forks absorb braking bumps so much better. i did not make any valving changes and started with the clickers in the same position i had them at with the old springs. (1 change at a time). had to slow the rebound down a couple clicks in and went 2 clicks out on comp also. the only change i made was started with lower oil height @ 325mm and never bottomed out once. i even purposely flat landed and cased a couple jumps, just to feel it out. still about 1.5" from full bottom. These springs are about 1 size to stiff, from Racetech calculator. the only negative thing i noticed was flat rough sweeping corner, the forks deflected off the bumps and pushed me outside.

i will continue to play with the clickers and test. Thanks for your help everyone.

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6 hours ago, asian195 said:

i know numroe said this, but wouldn't that flex the shims? would measuring the gap between the last shim/spacer and spring cup be ideal?

No. The shims dont flex when doing this. You push the feeler gauge into to touch the shaft. It'll either fit or not.  Very quick and easy. Use two feelers of the same thickness from opposite sides if you don't trust your technique.

If you measure between the 17.3 and the cup then you could be measuring shim flex.

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get heavier springs. pull the crossover out of the base valve.  start with lower oil level and work up to combat bottoming.

This was my first thought exactly.

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On 7/14/2017 at 4:25 AM, numroe said:

No. The shims dont flex when doing this. You push the feeler gauge into to touch the shaft. It'll either fit or not.  Very quick and easy. Use two feelers of the same thickness from opposite sides if you don't trust your technique.

If you measure between the 17.3 and the cup then you could be measuring shim flex.

ok cool. Thanks. will do next time i have them apart.

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