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KYB mid valve help


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Hi everyone,

I've just pulled down my KYB orks for a service and to play with the valving. This is my first time tuning shims.

The mid valve was not what I expected, can anyone help me understand it? There is no progressive stack just 3x 20s. I've been reading up on TT about stacks but I'm not sure what advantage of this stack is. Is it just to soften the mid valve?

MV

20(x3) 0.11

11(x2) 0.3

14(x1) 0.2

15(x1)0.3

17(x1)0.3

 

 

 

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6 hours ago, Rb03 said:

Hi everyone,

I've just pulled down my KYB orks for a service and to play with the valving. This is my first time tuning shims.

The mid valve was not what I expected, can anyone help me understand it? There is no progressive stack just 3x 20s. I've been reading up on TT about stacks but I'm not sure what advantage of this stack is. Is it just to soften the mid valve?

MV

20(x3) 0.11

11(x2) 0.3

14(x1) 0.2

15(x1)0.3

17(x1)0.3

 

 

 

Are you offroad or motocross?   What bike and skill level?

That's a pretty light stack if there's any float going on at all.

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7 hours ago, mog said:

What's the float ?

I just measured it, around 0.43mm

 

6 hours ago, cwtoyota said:

Are you offroad or motocross?   What bike and skill level?

That's a pretty light stack if there's any float going on at all.

Offroad single track and rocky. I'm an average rider not racing.

The bike is a 13 Gasgas ec300.

 

The forks are a bit harsh in HS compression but also have a fair bit of brake dive.

 

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You need more max opening on the midvalve to get rid of the high speed harshness. Shim under the collar a total thickness of .6mm under the collar. Those will be 8OD x 6 ID shims. Then add another 11.3 or a 10.3 next to the other 11's and add some taper to the top of the stack so the upper shims have a smooth bend instead of developing a kink from all the bend happening at the edge of the 11's. So add 18.1, 16.1, 14.1 below the 20s. Keep your float around the same and stiffen up the base valve to handle the brake dive. 

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I agree with jjy130's suggestion.

A more typical setting will give you better hold-up and still allow the fork to take the edge off of the square edges & roots.
An OEM stack in a 24mm KYB cartridge for a Yamaha motocross setting looks like this:

Piston
3@20.11
18.11
16.11
14.11
12.11
10.20
17.30
Sleeve, & cup
post

There's a huge thread floating around the forum regarding Yamaha KYB SSS off-road revalve settings.  Read through some of that if you have time.

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2 hours ago, jjy130 said:

You need more max opening on the midvalve to get rid of the high speed harshness. Shim under the collar a total thickness of .6mm under the collar. Those will be 8OD x 6 ID shims. Then add another 11.3 or a 10.3 next to the other 11's and add some taper to the top of the stack so the upper shims have a smooth bend instead of developing a kink from all the bend happening at the edge of the 11's. So add 18.1, 16.1, 14.1 below the 20s. Keep your float around the same and stiffen up the base valve to handle the brake dive. 

Thanks for the info. I'm very much still learning, are the  shims under the collar you are referring to the ones called "extender shims" in the diagram ?

Screenshot_20210814-044447__01.jpg

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2 hours ago, cwtoyota said:

I agree with jjy130's suggestion.

A more typical setting will give you better hold-up and still allow the fork to take the edge off of the square edges & roots.
An OEM stack in a 24mm KYB cartridge for a Yamaha motocross setting looks like this:

Piston
3@20.11
18.11
16.11
14.11
12.11
10.20
17.30
Sleeve, & cup
post

There's a huge thread floating around the forum regarding Yamaha KYB SSS off-road revalve settings.  Read through some of that if you have time.

Thanks, I started reading that thread but got lost in it all

 

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5 hours ago, Rb03 said:

Thanks for the info. I'm very much still learning, are the  shims under the collar you are referring to the ones called "extender shims" in the diagram ?

Screenshot_20210814-044447__01.jpg

Yes, but you want to put them under the collar inside the cup instead of at the top against the piston. 

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5 hours ago, Rb03 said:

Thanks for the info. I'm very much still learning, are the  shims under the collar you are referring to the ones called "extender shims" in the diagram ?

Screenshot_20210814-044447__01.jpg

Your 17.3 stop-shim tells me that you probably don't have a single piece sleeve-washer as shown in that diagram.
The 17mm KYB cup uses a seperate 8mm OD, 6mm ID 5.3mm long sleeve.  
The other style is a 20mm KYB cup and sleeve are integral (one piece) with the threaded post.

Your 6mm id spacer shims would go between the cup and sleeve on your setup if the cup and sleeve are separate pieces.

 

 

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The reason for the tapered stack is durability.  Having these three face shims directly clamped by the 11mm shims causes the 20's to bend from just outside the clamp.  This can cause the shims to kink, deform and break.

A proper tapered stack can generate the same damping you have now or any damping you like while properly supporting the face shims so you don't have to worry about wearing out or damaging the stack.

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  • 2 weeks later...
On 8/14/2021 at 10:49 AM, jjy130 said:

Yes, but you want to put them under the collar inside the cup instead of at the top against the piston. 

 Okay I'll check it out when i can get out to the shed

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On 8/14/2021 at 10:51 AM, cwtoyota said:

Your 17.3 stop-shim tells me that you probably don't have a single piece sleeve-washer as shown in that diagram.
The 17mm KYB cup uses a seperate 8mm OD, 6mm ID 5.3mm long sleeve.  
The other style is a 20mm KYB cup and sleeve are integral (one piece) with the threaded post.

Your 6mm id spacer shims would go between the cup and sleeve on your setup if the cup and sleeve are separate pieces.

 

 

Okay thanks, Im hoping that will make more sense to me when I go and look at the stack again.

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On 8/15/2021 at 5:33 AM, turbo dan said:

The reason for the tapered stack is durability.  Having these three face shims directly clamped by the 11mm shims causes the 20's to bend from just outside the clamp.  This can cause the shims to kink, deform and break.

A proper tapered stack can generate the same damping you have now or any damping you like while properly supporting the face shims so you don't have to worry about wearing out or damaging the stack.

Yep that makes sense. I will have to track down some shims. Any suggestions on where to buy that's not workshop quantities?

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I have purchased from SDI as well.  Doesn't hurt to order enough to put together a little starter shim kit.  It's like carb jets, you might not need all those other ones right now but later on you will probably find a use for them.

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10 hours ago, Rb03 said:

Yep that makes sense. I will have to track down some shims. Any suggestions on where to buy that's not workshop quantities?

Like the other guys said, SDI is a good choice.  
I've never tried Slavens, but never heard a single bad thing about them.


SDI is Suspension Direct, here's a link:
https://www.suspensiondirect.com/shop/shim-parts/3-8mm-id-shims/a-0-10-thickness

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