What do these shims do?

[jossbuk]

I have noticed that two extra items have been added to the KTM front fork parts list for 2002. Items 49* 6x8.0x0.1(shim) and 6x8.0x0.3(shim) have been added to item 49 8x24x0.1 4off (check valve) on the rebound piston. What do these do? Why is the ID of the check vale 8 and the shims 6? Do they stop the check valve from touching the piston face? Why do that? Should I change my 2000 200exc to be the same?

Can anyone shine a light on this one. I can guess what they do but have never taken 2002 forks apart YET!!!

regards

Joss :(

 

[Bud-Man]

jossbuk,
The 6x8x.10 and 6x8x.3 shims fit down into a counterbore on the rebound piston (on the mid-valve or check plate side). These shims act as a spacer to give the mid-valve/check plate more lift. The amount of lift in the mid-valve determines at what fork speed the valving becomes acitve. As for weather or not you should use these spacers.....well that is complicated. Probably not. Changing one aspect of the forks valving without taking into consideration other issues may make the fork work worse. More likely, you will go through a lot of effort and not notice much or any difference ;) .

 

[jossbuk]

Thanks. Now I understand what they do. Although they are not present on the 2000 200ktm exc part list, One of these shims is used the way you point out.

I understand what the check plate is(not sure why they use 4 shims). That is the other side of the piston to the compression stack. But when is a check valve called a mid-valve?

I have more questions but I will try one thing at a time
Wh

 

[marcusgunby]

The 4 shims are the midvalve(on the back of the rebound side of the piston)-it makes it tunable, a plate you can do nothing with, when you have shims you can go stiffer/softer. more/less lift, more high speed compression etc.

 

[jossbuk]

Thanks for that Marcus. I could say that I was only testing when I said compression pistonbut I would be lieing...

And theres more... The 02 forks I noticed use a 0.5 check valve spring and the earlier forks use 0.25 checkvalve/midvale springs. The other components remain the same ( 4off 0.1mm shims)... What would be the purpose of this? has anybody modified this area on the WP forks.

 

[jossbuk]

Wow!!! I just read the "Thinking out loud about forks" threads about 10 times. Each time I read it I learn more...