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First attempt at shim changes

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First my info, 170 lb(no gear) B desert racer. 05 yz250. .44 (stock) springs. 12 out on both the rebound and comp and 225cc of oil in the outer chamber. I figure the stock springs are ok because of the additional gas from the oversized tank (3.2 gallons total). We have miles of sandy whoops and many sections of fist sized and bigger square edged rocks, these are the two things that seem to wear me down the most.

I figure this means I dont really want to touch the LS compression much because of the whoops although some additional plushness would be nice to soak up all the chop. Here is what I am considering to start with.

Base valve:

24 x .1 (9) -> split the stack with the 18 x .1

22 x .1 -> remove

20 x .1

18 x .1 -> remove

14 x .1

11 x .25

18 x .5 (2)

What worries me the most is that there are so few shims to begin with. The only stuff I have really been able to learn has all been for showas which have way more shims.

Let me know how this would be for a start.

Thanks,

Robby

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First my info, 170 lb(no gear) B desert racer. 05 yz250. .44 (stock) springs. 12 out on both the rebound and comp and 225cc of oil in the outer chamber. I figure the stock springs are ok because of the additional gas from the oversized tank (3.2 gallons total). We have miles of sandy whoops and many sections of fist sized and bigger square edged rocks, these are the two things that seem to wear me down the most.

I figure this means I dont really want to touch the LS compression much because of the whoops although some additional plushness would be nice to soak up all the chop. Here is what I am considering to start with.

Base valve:

24 x .1 (9) -> split the stack with the 18 x .1

22 x .1 -> remove

20 x .1

18 x .1 -> remove

14 x .1

11 x .25

18 x .5 (2)

What worries me the most is that there are so few shims to begin with. The only stuff I have really been able to learn has all been for showas which have way more shims.

Let me know how this would be for a start.

Thanks,

Robby

how much shims depends on shims diameter, thickness (showa shims are 0.1mm - KYB shims are 0.115mm), piston rod diameter and valving itself.

if you want only plusher low-speed then you can split the stack. but seems you have trouble with square edged rocks, I would not recommend to split it, just take out a few shims and this makes high and low speed softer. if you split it, you make the low speed more softer compared to high speed.

just take out the shims you wrote and I'll bet your fork works much better than before. if you think it's still too harsh, remove one or two of the 24mm shims.

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I was thinking that splitting the low speed stack would make it just a little plusher at the beginning of the low speed by getting them to move a little sooner and then firm up a little at slightly higher shaft speeds but I think I see what you are saying, this might cause a funny little spike in between the low and high speeds. What about using the 22 as a bleed?

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I think it's ok to split it as a bleed (means you put the bleed shim in second position). then the 18 .1 will be ok, the 22 .1 is ok too (less effect).

are you able to ride now or do you have winter like the east coast guys?

if you can ride just do the changes and post the result. most guys ask here for a revalve, they get thousands of answers and advice and then the thread is dead and no one knows what he did, did it work properly...?

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I think it's ok to split it as a bleed (means you put the bleed shim in second position). then the 18 .1 will be ok, the 22 .1 is ok too (less effect).

are you able to ride now or do you have winter like the east coast guys?

if you can ride just do the changes and post the result. most guys ask here for a revalve, they get thousands of answers and advice and then the thread is dead and knowone knows what he did, did it work properly...?

I can ride right now, in fact, I have a 100 mile race Sunday. I think I am going to go ahead and go for it but probably just remove the to HS shims as I think removing the 22 will end up letting the LS shims deflect a little easier and I don't want things to get to soft. I would like to det rid of the pinballing I have in rock sections but we have TONS of sandy whoops and I am worried that if the LS gets to soft I will be miserable. Thanks a lot for you input, I have had next to no luck with most of my posts. I will let you know how things go. I should be able to go out for a short testing day on Saturday.

Robby

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ok, but if you remove two HS shims the LS will be also much softer because the 24mm shims can bend easier. I think it will work and feel free to do what you want :applause:

I would recommend to take out 3 of the 24mm shims but I repeat - your proposal will also work!

in general, with a crossover shim you really have HS and LS shims, without a crossover you don't have! that's my opinion and that's the result of a test with different shim stacks I made on a hydraulic machine. the curve of a conventional shim stack was not that different to the curve of the stack with only one size shims.

so, you can take out the big ones or the "HS" shims, you will get a softer damping in both high and low speed.

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So you are saying that unless the 24mm shims are seperated from the rest of the stack by a smaller shim (crossover) the stack isnt really seperated into high and low speed shims. It seems like this forks adjustibility is really limited due to its small number of shims, is this true? Do you think removing 4 of the 24s would adversly effect the way my bike handles in whoops?

It seems like to make the fork more adjustable you would need to remove an 18 x .5 and use more/thinner shims.

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I don't think it's limited due to small number of shims, if you take out only one shim it will become just slightly softer. the new forks have bigger diameter shims (Showa 30mm, KYB 32mm), that bigger diameter causes more "leverage" so you have to use more shims. IMO more shims works better but for the old small style shim stacks you would need thinner shims, which I don't know where or if you can get them.

I don't know if removing 4 of the 24s would adversly effect the way your bike handles in whoops, but as I said, I recommend to remove 3 of the 24s

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I have a YZF-450 with the same forks and have tried a few things. I also do not like the amount of shims as it seems to limit things. You may be to light on low speed removing more than one of the 24mm shims if you have not done anything to the mid-valve. I really liked my forks when I removed the

20mm shim. You might try that first as it really made the forks move well, I think I am going back to it next time I have them apart.

It is a shame that more people do not post the results of their stacks. I am guilty as well, as soon as I fix my problem I kind of drop the post.

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I have a YZF-450 with the same forks and have tried a few things. I also do not like the amount of shims as it seems to limit things. You may be to light on low speed removing more than one of the 24mm shims if you have not done anything to the mid-valve. I really liked my forks when I removed the

20mm shim. You might try that first as it really made the forks move well, I think I am going back to it next time I have them apart.

It is a shame that more people do not post the results of their stacks. I am guilty as well, as soon as I fix my problem I kind of drop the post.

I was considering removing the 20 as that seems like the most logical HS shim to remove, making the the taper linear (each HS shim being 4mm difference). Could you notice a difference just removing 1 shim? What was the issue you were trying to resolve? Did you also make changes to your mid-valve, springs, ICS, etc?

I think I am going to hold off on the revalve for a week or so. I want to try and break out the camcorder and get some footage of me riding through the type of terrain that gives me trouble and really get a handle on what the bike is doing. Either way, I will defiantly stay with the thread until I get it figured out.

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I was considering removing the 20 as that seems like the most logical HS shim to remove, making the the taper linear (each HS shim being 4mm difference). Could you notice a difference just removing 1 shim? What was the issue you were trying to resolve? Did you also make changes to your mid-valve, springs, ICS, etc?

I think I am going to hold off on the revalve for a week or so. I want to try and break out the camcorder and get some footage of me riding through the type of terrain that gives me trouble and really get a handle on what the bike is doing. Either way, I will defiantly stay with the thread until I get it figured out.

When I bought the bike it was used and set up for a fast B rider so I was trying to get it closer to what I needed. One shim can make more of a difference than you might think. I stiffened up the mid valve and did away with the bleed shim and they are working pretty good now. The mid valve stuff made more of a difference than anything but I liked the forks with the 20 removed.

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So I never got around to do any filming or anything but I did put in 4 desert races, a couple of GPs, and about 40 trail hours on my bike with the fork as follows.

Base Valve:

24 x .1 (7) -> removed two. Stock uses 9

22 x .1

20 x .1 -> Once I got in there I found that this shim was not there, I guess they changed the valving in the late 05s???

18 x .1

14 x .1

11 x .25

18 x .5 (2)

midvalve is stock:

16 x .10

22 x .08 (3)

18 x .08

16 x .08

14 x .08

12 x .25

16 x .10

22 x .40

Spring and Collar

10 x .20

15 x .20

Spring Cup

Clickers:

comp. 6-8 out depending on coarse speed

reb. 12 out

Oil:

260cc (stock 250cc)

I started with 225cc of oil thinking it would help the square edged stuff but I was blowing through the stroke.

Removing the two base valve shims definitely helped without making it mushy but it still dances through the rocks more than I would like and it dives too much when I use the front brakes. I think it is time to start playing with the mid and would like some suggestions. My goals are to keep the bike up in the stroke more when cornering and braking hard into the corner and most of all track through the rocky sections rather than deflecting every which way. I am still considering sending the forks out but what to give it a few more shots first.

Thanks

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There are a lot of things that need to be done on the 05 forks to fix them. If you do a search in this forum you will find most of the fixes. I would put the compression stack back to stock until you get closer. You need to work on the mid-valve, remove the 16mm bleed shim, add a 22.1 shim and remove the 10.20 under the collar. This will help with the diving problem as long as you have bled the cartridge correctly. These forks also have a main spring that is to short [not enough pre-load] and the ICS spring needs a spacer.

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I have done the spacers already but thanks for the suggestions. Removing the bleed and throwing in the 22 makes sense to stop the diving. Would I be increasing the float by removing the 10 x .2 under the collar? It seems like although the increase in float will help smooth things out, the fork will be all around stiffer than stock (with the base shims replaced).

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Ya, the 05s used less oil, 200-300ml (stock 250ml). The 05s were the first year of twin chambers, they made many revisions for 06.

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I have done the spacers already but thanks for the suggestions. Removing the bleed and throwing in the 22 makes sense to stop the diving. Would I be increasing the float by removing the 10 x .2 under the collar? It seems like although the increase in float will help smooth things out, the fork will be all around stiffer than stock (with the base shims replaced).

I was always afraid the the mid-valve would make the fork stiff but beleive me it will not. You are actually tightening up the float distance by removing the 10.2 and it really helps. The stock base valving should be close to start. You could even add a 12.1 at the end of the stack with no problem. I spent a lot of time on these forks on my 450 and have them working really well. A couple of other things that worked well was the Factory Connection oil lock collars with 220ml to 250 ml Moble-1 synthetic ATF in the outer chamber. I could tell a difference when I put this stuff in.

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I was always afraid the the mid-valve would make the fork stiff but beleive me it will not. You are actually tightening up the float distance by removing the 10.2 and it really helps. The stock base valving should be close to start. You could even add a 12.1 at the end of the stack with no problem. I spent a lot of time on these forks on my 450 and have them working really well. A couple of other things that worked well was the Factory Connection oil lock collars with 220ml to 250 ml Moble-1 synthetic ATF in the outer chamber. I could tell a difference when I put this stuff in.

I understand how these changes will help keep the bike up in the stroke but not how they will help my initial complaint, square edge rocks. The first changes I made are the ones that cause the new problem, diving, and they did only a little to help the first problem. I also dont understand how removing the 12 x .2 will decrease the float as it is increasing the distance between the last shim in the stack and the bottom of the collar. Dont get me wrong, I appreciate your input, especially since it is the only input I am getting, I am just a little confused by your suggestions.

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I understand how these changes will help keep the bike up in the stroke but not how they will help my initial complaint, square edge rocks. The first changes I made are the ones that cause the new problem, diving, and they did only a little to help the first problem. I also dont understand how removing the 12 x .2 will decrease the float as it is increasing the distance between the last shim in the stack and the bottom of the collar. Dont get me wrong, I appreciate your input, especially since it is the only input I am getting, I am just a little confused by your suggestions.

If you look at the location of the 10.2 shim {not 12.2 as you wrote} it is above the collar between the collar and cupped washer in the mid-valve. By removing it the distance the shims move before they deflect is less. The 12.1 shim I was talking about adding would be in the compression stack under the 14.1

Try these few things and I think you will be surprised, I spent a lot of time trying not to firm things up and the forks were always as you described. Deflecting off of everything and diving at the same time.

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I have a set of 05 KYB's from a 250f on my 03KX250. I have removed the spring and washers that provide the seal/valve between the two chambers. As far as I have read this is a good mod for these forks and really takes away the harshness that is inherent in these forks.

I am curious as well... why put a different type of oil in the upper chamber when in very little time the two oils will mix? The chambers are not 100% seperate from one another as I see it. Am I wrong in my thinking?

Thanks,

John

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