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Van Wick

CRF250X - My Fork Stack Mods, need advise

41 posts in this topic

I need some advise and guidance on the current fork stacks I'm testing. 

Trying to dial out deflections and get the forks more plush in the rocks but keep them stable for the faster single track (hard pack) riding with square edge bumps. 
Forks are starting to feel better, still not perfect yet as I have tried a few different shim stack including several changes to the BV, Rebound and Mid Valve. Have tried everything from smaller BV Comp cross overs with less face shims to lowers floats (0.15) with lighter MV comp stacks.

 

I'm starting to get a little lost on get it dialed in properly, changes that I've been making are all starting to feel the same and would appreciate some advise.

 

Bike: 2012 CRF250X

Rider: 185lbs with no gear

Intermediate Rider - ride mostly technical enduro, rocks and hard pack with lots of square edge bumps. No big jumps!

 

Forks:

Springs: 0.46 with 4mm preload (also have stock 0.42 and a set of 0.44 springs - have not tested with these yet)
SKF Oil Seal and Wiper kit, New OEM Bushes replaced recently.

Oil Height: 375cc 5wt Maxima Blue Bottle (played around with different oil volumes from 340ml to 375ml, have not tried lower oil)
Comp:8-9
Reb:13-15
 

BV

30.1 x4
28.1 cardinale199 uses a cross over like this on single stage stacks for MX for initial LS plushness on small bumps - thought I'd try it
30.1 x8
27.1
29.1
28.1
26.1
24.1
22.1
20.1
18.1
16.1
14.2
14.2
14.2
14.2
 
MV
20.1 x3
18.1
17.1
16.1
10.2 x2
11.3
 
Post = 1.95mm
Float 0.35
 
REB
20.1 stock is 20.1, 19.1, 18.1, 12.1 (cross over)
20.1
19.1
12.1
18.1  added the 18.1 for more HSR damping and removed the 13.1
16.1
14.1
12.1
11.1
16.3
16.3
16.3
16.3
 

Shock:

Shock is currently stock valving, think I need to considering re-valving the shock as well, not sure yet on what I would change - any advise on shock stacks that would work would also be appreciated.

 

Have noticed that running the rebound faster on the shock helps a lot with front end plushness and reduces deflection on the forks.

 

Springs: 5.3

Race Sag : 108mm | Static Sag: 32mm

LSC: 14

HSC: 3
Reb:13

 
With this current fork stack setup I have some handling issues, forks feel plush but I need to run the LC clickers @ 8-9 to keep the front stable when riding at pace. In slow tech riding the forks feel good. Rebound @ 13-15 also work well and reduce deflection riding at a slower pace. But the Rebound is a little fast and pops the front wheel up on small dog size bumps and other obstacles and I end up on the back wheel when riding at pace - lots of fun but does get scary every now and then.
 
If I slow the rebound down to counter act the effect of the forks popping up the forks get harsh and choppy again. On the comp clickers if I open the clickers the forks also get harsh and the bikes feels like it does not turn as good, with LS Comp clickers open @ 14-16 for comfort I can then go in on Rebound @ 10-11 clicks but these setting does not feel as plush and stable as the clickers settings that are the other way around. 

My challenge is mainly with the mid valve and rebound, have an idea of what needs to be done but not 100% sure if my current settings work in balance with the BV, MV and Reb.
 
I think the solution to correct the problems could be as simple as closing the float to 0.30 with the current MV stack and taking the rebound back to a stock.
 
This is my 5th attempt at revalving the forks, am I close or are my stacks just plan wacky?
 
Edited by Van Wick

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You could try this combo, it works great!

Preload 4mm

Oil 360ml maxima 5w fluid

Base valve stack

All shims 0.1mm thick

30x3

22

30

29

28

27

26

25

24

23

22

21

20

19

18

17

16

15

14

30 x 2mm washer

Mid float 0.2

20x3

18

17

16

14

12

12x2mm washer. remove17mm (alloy washer spring retainer) but keep spring,(it adds to much restriction in the high fork speed!

Rebound stock

Base set at 8 clicks out and reb 12 out

Rear shock leave main shim stacks stock ( comp & reb) , work on the ( high low speed adjuster assembly ) now dismantle the adjuster to adjust the shim stack , remove 1 of the smallest clamp shims from the bottom of the stack and put it between the 1st and second face shims, run the high speed adjuster 1 turn out , low speed 12 and reb 11 out.

Enjoy

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Interesting stack arrangement you have.

 

Seems odd but does look like it could work, few questions though if you don't mind.

 

Is the BV stack not to soft or does it rely on the progression of the taper to control the damping?

Basically you have a tapered stack with more HS shims to make up for the lack of low speed face shims or is the low speed missing some face shims - you list 3 x shims before the 22.1 cross over, is that correct?

 

The Mid Valve has me scratching my head, I get that you are removing the washer spring retainer cup, only problem is my Mid Valve cup has a OD of 19.3mm and you listed a 17mm.

 

If I took this out and put in a 12x2mm washer, what does the spring rest on and what is going to stop it from moving?

My MV springs is ID=13.5mm and OD=14.5mm.

 

Can't recall what OD the post underneath the spring cup is, does the spring rest on the post then?

What stops the spring from moving around though  :eek:

 

The 12.1 shim is not in contact with the spring and the 14.1 shim is barely fitting on top of my MV spring - already tried a taper stack like this with 0.20 float. When I tried this my thought was that I needed a different MV Spring with a smaller ID to interface with the 14.1 shim better, could not figure out how or if the 14.1 shim actually deflects. The 12.1 would therefore become a packing shim like Race Tech use in there MV stacks as it basically sits inside the MV spring?

 

I believe the KYB forks have the narrower spring and have seen a Racetech MV Kit that also uses a smaller cup and spring. Does not seem like this MV stack style is designed to work on a CRF250X's MV setup, the X's forks use the pre 2008 Showa MV design.

 
Shock mod on the high low speed adjuster assembly sounds like a simple straight forward fix for for getting the Hi Speed problem sorted without having to go into main stack to do a serious shim shuffle.
I'm willing to test this out as a first attempt - might be all that is needed.

 

Looking through my previous re-valve stack notes now, I realized that your stack suggestion is very similar to my first re-valve attempt, only difference was I had more LS shims on the BV: 13x 30.1, 24.1 (x-over), then same HSC stack down but minus all the odd numbered shims from 26.1 down. My MV was also similar except I had 18.1, 16.1, 14.1 , 12.1 and smaller 9.5 clamps.

I did not like that setup, forks felt inconsistent on repetitive square edge hits.

Edited by Van Wick

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i was racing on cross country race here . is 90 minutes race . laptime 8-9minutes , one lap of mx track and 7 minutes of rocks , line woods , sand, river rocks , and many obstacle

 

my best stack was

30.10x18 to 22 faceshim

28.10

26.10

24.10

22.10

20.10

18.10

16.10

14.10

12.20x3

 

midvalve 20.10x4

17.10x4

and 0.20float

 

rebound

20.10x2

14.10

18.10

16.10

14.10

12.10

11.10

spring 0.45 with 10mm preload  oil 300cc

im 87kg 

on shock 5.3spring

44.20 x 16

34.15

30.10

44.20

42.20

40.20

38.20

36.20

34.20

32.20

30.20

28.20

26.20

24.20

22.20

20.30x3

rebound

40.20x4

28.10

40.30

38.30

36.30

34.30

32.30

30.30

28.30

26.30

24.30

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cardinale199 I was hoping you would give your opinion. I have been following a lot of your posts, your thought on tuning are very interesting and practical. 

See so many stacks are less LS shims on the BV and lighter MV for a heavier rider for enduro. If we increase spring rate for heavier rider surely the shims stacks should also be beefed up in the right places. 

 

No cross over for BV with stiffer LS Comp and lighter HS Comp with smaller 12.20 x3 clamp, wanted to try a single stage BV on my current stack but added cross overs at the last minute thinking it might be to stiff - secret is the smaller clamp  :banghead:

 

Run less oil (300ml), a local tuners has been suggesting that I use lower oil for enduro and less shims on rebound side too. He says the forks must move quickly for enduro rocks and roots.

 

You have also answered my question about the mid valve float, 0.20 seems to be a recommended float height on TT for these forks. I only tried a 0.20 float once but my BV and MV was very light so the overall performance of the forks on that re-valve was not good.

 

I have two questions:
Should I use my current MV clamp shim setup of 3x 10.2 or do I need less clamp height and smaller clamp shims for the stack you posted?

Must I still reverse stack the spare BV shims after the clamp to keep the BV height?

 

Thanks for the shock stacks to try out :thumbsup:  I will try both forks and shock settings and give some feedback after testing.

Will only be able to make the changes next week though and test ride next weekend.

Edited by Van Wick

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I f  a base stack doesn,t open far enough to contact a backer,then there is no difference between removing base shims or decreasing the clamp size.seems a lot of folks on here think putting in a small clamp some how reduces high speed but keeps the low speed intact.it doesn,t .a smaller clamp makes the whole stack softer.removing face shims makes the whole stack softer.works out the same.

Edited by cj_wai
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cj-waj, that was my understanding as well of a smaller clamp versus lesser base shims, that the overall stack will become softer LS and HS. Several good threads here on TT that cover the topic.

 

Single stage stack from what I have read should provide more consistency versus 2 stage, even for enduro use. The stock CRF250X BV stacks are so close to what Cardinale199 has suggested:

30.1 x14 

27.1

29.1 x2

28.1 x2

 

with a rather large 27.1 cross over separating the 30's from the two 29's and 28's the stock BV is almost a single stage. Remove the 27.01 x-over and I'm sure it would ride very close Cardinale199 setting.

It's basically the HS Comp on the BV that needs some slight tweaking on the Showa forks and already it will be a good improvement.

 

Starting to think that I could have achieved pretty good results on my first re-valve by simple reducing the clamp size on the stock BV, running lighter 2.5w oil in the cartridge and a lower oil height. The lighter 2.5w oil would also speed up the stock rebound, faster rebound I have noticed address deflection and the lower outer oil level would soften the transition into the mid valve for an overall plusher more compliant ride than the stock settings.

 

Plush and compliant does not necessarily always mean softer, I have been going softer and softer with each re-valve I have done hence why every time I made a change it felt the same or similar.

 

Personally I don't have enough experience to put all the theory into practice, getting there slowly but surely.

Thankful for the advise available on TT.

Edited by Van Wick

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The Mid Valve has me scratching my head, I get that you are removing the washer spring retainer cup, only problem is my Mid Valve cup has a OD of 19.3mm and you listed a 17mm.

 

If I took this out and put in a 12x2mm washer, what does the spring rest on and what is going to stop it from moving?

My MV springs is ID=13.5mm and OD=14.5mm.

 

 

The crucial question is:

Is it a Showa 47 style cartridge or a showa 48 style aka KYB?

 

I think that trekxrr is talking about a kyb style mid whereas you are talking about a showa style mv.

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Interesting stack arrangement you have.

 

Seems odd but does look like it could work, few questions though if you don't mind.

 

Is the BV stack not to soft or does it rely on the progression of the taper to control the damping?

Basically you have a tapered stack with more HS shims to make up for the lack of low speed face shims or is the low speed missing some face shims - you list 3 x shims before the 22.1 cross over, is that correct?

 

The Mid Valve has me scratching my head, I get that you are removing the washer spring retainer cup, only problem is my Mid Valve cup has a OD of 19.3mm and you listed a 17mm.

 

If I took this out and put in a 12x2mm washer, what does the spring rest on and what is going to stop it from moving?

My MV springs is ID=13.5mm and OD=14.5mm.

 

Can't recall what OD the post underneath the spring cup is, does the spring rest on the post then?

What stops the spring from moving around though  :eek:

 

The 12.1 shim is not in contact with the spring and the 14.1 shim is barely fitting on top of my MV spring - already tried a taper stack like this with 0.20 float. When I tried this my thought was that I needed a different MV Spring with a smaller ID to interface with the 14.1 shim better, could not figure out how or if the 14.1 shim actually deflects. The 12.1 would therefore become a packing shim like Race Tech use in there MV stacks as it basically sits inside the MV spring?

 

I believe the KYB forks have the narrower spring and have seen a Racetech MV Kit that also uses a smaller cup and spring. Does not seem like this MV stack style is designed to work on a CRF250X's MV setup, the X's forks use the pre 2008 Showa MV design.

 

Shock mod on the high low speed adjuster assembly sounds like a simple straight forward fix for for getting the Hi Speed problem sorted without having to go into main stack to do a serious shim shuffle.

I'm willing to test this out as a first attempt - might be all that is needed.

 

Looking through my previous re-valve stack notes now, I realized that your stack suggestion is very similar to my first re-valve attempt, only difference was I had more LS shims on the BV: 13x 30.1, 24.1 (x-over), then same HSC stack down but minus all the odd numbered shims from 26.1 down. My MV was also similar except I had 18.1, 16.1, 14.1 , 12.1 and smaller 9.5 clamps.

I did not like that setup, forks felt inconsistent on repetitive square edge hits.

Yep with the mid valve the cup is 19 mm,... I run the shim stack then at the clamp I fit a 12.3 mm x 2.5 mm washer then a 16 x 0.3mm shim to hold the spring up against the face shims, then I run 1 more 12.3 x 2.5 mm washer.

With the base valve set up i used this as the stock shim stack deflected off everything ! The balance between the mid and base work great! All you can do is try it or not!

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The crucial question is:

Is it a Showa 47 style cartridge or a showa 48 style aka KYB?

 

I think that trekxrr is talking about a kyb style mid whereas you are talking about a showa style mv.

Sorry for the mix up

My setup is for 47mm showa's.......

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Okay, than I honestly dont know what you do, haha!

Could you elaborate this a bit more, please?

 

Pics would be awesome. If you dont have some, maybe a stack description brings more light into my darkness.

 

Let's say the stock mv is the following:

4x20.1 ID8

3x17.1 ID8

collar: ID 6xOD 8x1.88 height

soft showa mv spring

10.2 ID6

2x11.2 ID6

Spring retainer cup

 

How does your stack look like?

Edited by Vietze

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Okay, than I honestly dont know what you do, haha!

Could you elaborate this a bit more, please?

 

Pics would be awesome. If you dont have some, maybe a stack description brings more light into my darkness.

 

Let's say the stock mv is the following:

4x20.1 ID8

3x17.1 ID8

soft showa mv spring

10.2 ID6

2x11.2 ID6

Spring retainer cup

 

How does your stack look like?

How do I post a pic??

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The easiest way is to upload the pic on imageshack.us and post the forum's link here!

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Agree with Vietze.
Trekxrr your stack suggestion is different and interesting and as I mentioned I would be open to trying it. The Mid Valve does need further explanation though

I have read about a similar MV setup somewhere, cant reminder where or which forum about removing the MV Cup Washer to improve flow.

Is this your mid valve stack?

 

Mid float 0.2 
20.1 x3
18.1
17.1

16.1
14.1
12.1
12.3x2mm washer

16.3

12.3x2mm washer
Post = 2.00 correct?

So the MV spring rests on the 16.3, the 12.3x2 washer above that 16 is what hold the springs centered?
But how does that 12.3 washer hold the spring securely if the MV Spring's ID is 13.5mm?

 

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Agree with Vietze.

Trekxrr your stack suggestion is different and interesting and as I mentioned I would be open to trying it. The Mid Valve does need further explanation though

I have read about a similar MV setup somewhere, cant reminder where or which forum about removing the MV Cup Washer to improve flow.

Is this your mid valve stack?

 

Mid float 0.2 20.1 x318.117.1

16.114.112.112.3x2mm washer

16.3

12.3x2mm washerPost = 2.00 correct?So the MV spring rests on the 16.3, the 12.3x2 washer above that 16 is what hold the springs centered?But how does that 12.3 washer hold the spring securely if the MV Spring's ID is 13.5mm?

Yep just like that! 1mm ish free movement - 0.5 each side!

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Suppose one could try and find a 13.5mm OD washer to tighten up the free play.

These washers you refer to, are these standard hardware store bought washers?
 

 

The 12.1 shim is not in contact with the spring and the 14.1 shim is barely fitting on top of my MV spring - already tried a taper stack like this with 0.20 float. When I tried this my thought was that I needed a different MV Spring with a smaller ID to interface with the 14.1 shim better, could not figure out how or if the 14.1 shim actually deflects. The 12.1 would therefore become a packing shim like Race Tech use in there MV stacks as it basically sits inside the MV spring?

 

What about the 14.1 and 12.1 floating shims and how they interact with the spring?

I understand that the MV Floating shim deflect over the clamp shim, but with the 14.1 and spring OD of 14.5mm does the 14.1 shims even deflect at all.
And the 12.1 that lies inside the ID of the spring, there are a total of 8x MV Comp floating shims - the 12.1 is now a clamp shim and the 14.1 does not seem like it can deflect over the clamp so the 14.1 is now a clamp and all the shims above it deflect over the 14.1.

I'm not question the design, just don't understand how it works.

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trekxrr your from Aus, have read several of your posts on dirtbikeword.net.

You posted a similar BV stack on the CRF250X 2008 thread, recall you where using Goldvalve G2R valves at the time.

Does your stack need Goldvalves to work?
 

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damn , many post!! i used stock midvalve removing faceshim and adding little shim for close float to 0.20 cause i have crf 07 fork

 

about shim , on basevalve if you run only pair hs shim 0.10 yes shim can hit plate , i found on shim sign.

i use under base 12.30x3 but if you dont have enought 12 shim use 13 or 14 but always 12 clamp.

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damn , many post!!

Thread has grown long quickly, we have also been discussing discussing Trekxrr's MV shim stacks he posted in in post #3.

 

 

i used stock midvalve removing faceshim and adding little shim for close float to 0.20 cause i have crf 07 fork

 

I found the 07' CRF250R mid valve spec on valve stack index sticky, as listed below, so you are clamping on 2x 9.5 and 2x 10.20

I have these shims and spare MV posts and adjustments 8x6 shims, so I can replicate your suggested MV stack easy.

 

On the base valve, once you have your shim stack do you reverse stack the spare shims you took out of the hi speed stack (the way theDogger recommends)

Example:

 

30.10x18 to 22 faceshim

28.10

26.10

24.10

22.10

20.10

18.10

16.10

14.10

12.20x3 - Clamp

21.1   spare HS shim reverse stacked under clamp shim to keep base valve piston height same as stock height?

23.1

25.1

27.1

28.1

29.1

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yes u can flip hs stack also , i prefeer using 12.30x3 but wil be similar, i also use a 20mm plate exchange of oem 30mm bigger

 

important is use soft fork spring with more preload, bike will start stiff and finish soft.

 

0.46 4mm

i prefeer 0.44 10mm

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