shim shuffle - KTM WP forks Part 2

[bjalbert]

This Kinda goes along with everyone!
I have not seen anyone talk about the fork spring rate yet (I could be way off just let me know) I am fairly new to the suspension world but owning a KTM causes me to learn.
I just bought a 2001 KTM 125sx and the suspension is very harsh. I sent the rear shock to Pro-Action and had it revalved, but the front is still giving me a lot of headshake. I weigh 165 lbs. with gear. According to my friend at Pro-Action the fork rate on the front is way to soft to start with apparently it is more of a trail/enduro setup. I ride hard packed mx tracks with a lot of square edge bumps high speed straight a ways and breaking bumps. I was told that the front was riding to low so when you got on the bike you were already past the initial hit of the suspension, which causes the front end to pack.
The stock setup is .380 rate springs so I went to a .400 rate and I lighten up the rebound valving. This made a tremendous difference but it still feels harsh and I still get a little bit of headshake. I am using the stock compression valving.


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[marcusgunby]

If i remember correctly the std comp stack was a single stage set up that is good for control but can cause it to feel hard.It sounds like you would benefit from a revalve with a 2 stage stack.

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[bjalbert]

The stock stack is as follows:
6x24x0.10 x5
6x22x0.10 x1
6x20x0.10 x1
6x18x0.10 x1
6x16x0.10 x1
6x14x0.10 x1
6x11x0.15 x1
6x11x0.10 x1
6x18x0.25 x1

I am not sure if it is a single stage stack or a 2 stage stack. I am just now learning about how the shims work through out the stack.
thanks for the reply


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[marcusgunby]

That is a single stage stack as it has a pyramid shape to it with no cross over shim
ie a small one that separates the 6 24.1 from the rest of the stack.
The 2 11mm shims are there for the rest of the stack to bend around so if you made that say 13mm the whole stack will be alot stiffer and say if you fitted a 10mm instead the stack will be softer.The last 18mm shim is just a bottom out shim-it doesnt really do much.The thing you need to do is identify which part of the stack is wrong for you.If choppy bumps are the problem that may be High speed problems and you yould need to modify HSC which rougly speaking would be the shims after the 24.1's.Making them smaller would make high speed damping less.I think the 0.40 springs are the right way to go also what air gap are you using?Also another thing to try is 2.5wt oil instead of 5wt this will have an effect of making LSC less.

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[This message has been edited by marcusgunby (edited 04-20-2001).]

 

[bjalbert]

I am using a 130mm air gap with a 5 wt. oil. I do believe that my hsc is where my problem is because over high speed straights with square edge bumps the front end dances. it is to the point my lap times are down from when I owned my 99'.

The lsc seems pretty good and I have pretty good bottoming resistance. Where as with the .380 springs I used all the suspension even over small jumps.

so with my current stack how would I determine what a good hsc stack would be like. I like the sound of a two stage stack.
how would the following stack do in your opinion compared to the original.

6x24x0.10 x5
6x12x0.10 x1
6x20x0.10 x1
6x18x0.10 x1
6x16x0.10 x1
6x14x0.10 x1
6x11x0.15 x1
6x11x0.10 x1
6x18x0.25 x1

Thanks alot
Barry



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[JTT]

I may stand to be corrected here, but I would suggest that your proposed stack would significantly decrease LSC...opposite of what I think you are looking for.

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JTT
"Character is like a tree, and reputation is like it's shadow. The shadow is what we think of it, but the tree...the tree is the real thing."
Abe Lincoln

 

[bjalbert]

so the shims closest to the 6x24x0.10 are for LSC these are the shims that sit aginst the piston. now I am all confused I thought the first portion (i.e. the 6x24's) of the stack is for the initial hit or low speed and the middle of the stack is for the high speed stuff with the last portion of the stack for bottoming resistance.

Please direct me in the quest for good ktm suspension IS IT OUT THERE!!!

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[drehwurm]

Servus bjalbert,

Right now I am here in Greece testing my modified suspension. I had very much success increasing HSC to get rid of the deflecting. Even if it sounds strange the clue was to open a 'gap' in the HSC stack. Try replacing the 18x0.1 shim with a 20x0.1! Also I wouldn't decrease LSC too much, maybe just removing one of the 24x0.1 shim, but not more. How are your clickers set? Unfortunately I won't be back to my computer before next sunday, but give it a try!

Michael



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[bjalbert]

I will give it a try I just got back from riding. It is very hard to ride a rocket without any handling. right now I am at 27 clicks out on the comp. and 19 clicks on the rebound.

thanks for the help I will give it a try and let you know it will probably Tuesday before I get a chance to go out again.

thanks again this is a really awesome forum

Barry

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[marcusgunby]

I would try to help by saying if you put the 12mm crossover in you will reduce LSC too much unless you add some more 24.1's.Dont forget originally the 24.1's sat against the rest of the stack now they can bend over the 12mm crossover until they hit the rest of the stack.I would guess you will need 9*24.1 to get the same LSC with the crossover.That exact stack is the best one ive ridden on a KTM 125sx but i think the HSC was still to much-it jolted hard on slap down front wheel landings-i remember it well as i only rode the bike 4 hours ago :)I forgot to say we run 150mm air gap.

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[This message has been edited by marcusgunby (edited 04-21-2001).]

 

[bjalbert]

the exact stack being 9-24x.1's a 12x.1 and the rest of the stock stack. you said the HSC was still to much-it jolted hard on slap down front wheel landings. If you was going to revalve what would you change. I will try it and let you know I rode yesterday with the following stack:
4-24x.1
1-12x.1
1-20x.1
1-18x.1
1-17x.1
1-14x.1
1-12x.1
1-11x.15
1-11x.1
1-18x.25
what you said about lsc being to soft well on top of the 12x.1 causing the lsc to be softer I took out one of the 24x.1 (stupid I know)the bike was not ride able. It makes perfect sense that I would need more 24x.1's to keep the lsc up to par.

thanks
barry

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[marcusgunby]

I checked and i think it was
7*24.1(2*24.15=7*24.1 approx)
12.1
20.1
18.1
16.1
14.1
11.25
So the 2 extra 24.1's will help compensate for the 12mm cross over the 16 is smaller than the 17 you used and the 12.1 isnt used.Give us feedback on that stack and if HSC is too much then you could go to a 10.25 to reduce HSC-it will have a small effect on the total damping but it may be the answer.The 520 sx i beleive runs a similar HSC stack so i wouldnt think we need more HSC-but ive been wrong before and will be again.

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[drehwurm]

Servus bjalbert,

Just a few toughts:

.) If you are full out on the comp clicker it makes no sense to add 24x0.1 shims! I think you are going in the wrong direction - go in with the comp clickers and add shims if you have the feeling that the forks feel better the farther you close the clickers! Try it!

.) a 10x.25 shim instead of the 11x.25 will have a big effect - trust me on this one! It might work for your weight though.

.) I don't really understand why you want to compensate for the 12x.1 crossover shim! If you compensate for it, there is no use in using it at all. I'm running 5 24x.1 shims now and I'm heavier than you - 7 or even 9 seems not appropriate to me, but I'd be curious about the results if you try it.


Michael


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[marcusgunby]

drehwurm he hasnt said he is full out on comp with the new stack so im assuming his new stack is too soft on LSC and im not sure but i think 7*24.1 with a 12mm cross over will be softer than a std lsc set up(single stage)its a shame others cant ride a std ktm 125sx fork as it would be a good lesson on how not to valve a fork :)

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[drehwurm]

Servus Marcus,

In his last post he said something about '27 out on comp' which is almost full out I think. I'm, like you, of the oppinion that the KTM lacks LSC, but many are tempted to open the comp clickers to get rid of the harsh feeling, which in turn makes things only worse - you end up with a mushy and harsh fork ;)

its a shame others cant ride a std ktm 125sx fork as it would be a good lesson on how not to valve a fork

:) unfortunately I haven't had the pleasure, but if I get I chance I'll take it for scientific reasons ...

Michael


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[marcusgunby]

I hope my last post didnt sound offish as it wasnt meant to.

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[bjalbert]

sorry guys for not checking back sooner. I have been trying to get more shims ordered.

drehwurm,

I have 35 clicks on both rebound and compression this last stack i put in:
4-24x.1
1-12x.1
1-20x.1
1-18x.1
1-17x.1
1-14x.1
1-12x.1
1-11x.15
1-11x.1
1-18x.25
seemed better on the accel. bumps but the low speed stuff felt very very pogoie, and the turns seemed harder to stay in the ruts.
so would think (i could very well be wrong) that the lsc is to soft now.

I am thinking of trying the following stack since i can not get any shims right now.
6x24x0.10 x5
6x12x0.10 x1
6x20x0.10 x1
6x20x0.10 x1
6x16x0.10 x1
6x14x0.10 x1
6x11x0.15 x1
6x11x0.10 x1
6x18x0.25 x1

back on the 22nd you made this suggestion hopefully this is what you were talking.

Marcusgunby
I do agree if only more people could ride the stock bike it would be an eye opener. My brother-in-law races a honda and he rode it, He said "it was like riding a bull on steriods, it is so strong but out of control"

thanks for all the help I am not really sure where to go next with my shim stack. the springs and rebound valve changes I made along with the stock compression valving was the best so far but it had alot of high speed head shake it was very easy to out ride the suspension. my clickers in that senerio was comp. all the way in and the rebound at 18 along with a 130mm air gap.

Barry
2001 KTM 125 sx

 

[bjalbert]

In my previous post i said the comp. clickers were all the way in. What I was trying to say was it was all the way soft. That is why I wanted to soften my hsc. Softer on the clickers was a big improvemnet over full stiff.

sorry for the mix up if any.

barry

 

[drehwurm]

Servus bjalbert,

I have some comments:

1) Note that I'm using a thicker crossover 12x0.15 - this may make a big difference

2) I wouldn't run an oil level higher than 150mm if the fork is not bottoming

3) IMHO running any clicker too far in isn't usefull at all - I'll never go in farther than 6-8 clicks

4) I still think that replacing the 11x.25 with a 10x.25 might work for you!

Can you describe your symptoms a little closer - where do the problems arise and what problems? Does it happen in different situaions or just in special occasions ...

And again: don't expect answers - just pointers to find your own way!!!

Michael

 

[bjalbert]

It seems to only really have a problem on long straights with small to medium bumps. (third and fourth gear) the bars just want to slap from stop to stop. it also happens on approach to larger jumps (i.e. 70 - 80 ft.) everywhere else it feels fine.

thanks for the pointers, lately I have learned alot about suspension. that is my hobbie (bikes and tuning) so I am not looking for the quick answer learning is what I want. and the best way to do that is by hits and misses until you fully understand how things work.

barry

 

[bjalbert]

Also have a question does stacking two of the same diameter shims. do the same as adding one shim the same thickness as the two. I.E. 10x.10 x2 the same as 10x.2 x1 due to the lack of shims I was thinking I could stack two to get the right thickness. I would think that it would be the same.

barry

 

[drehwurm]

Servus barry,

In this case stacking is fine, because those shims don't bent. The distance from the base plate is the important factor!

You know, KTM's have had a reputation for headshake since a long time - and it is probaly not only suspension related, but to some extend a geometry problem. Get yourself a steering damper and be happy :cool:

Michael

 

[JTT]

Barry, Michael is right about the stacking of these particular shims, but stacking shims that are bending is a totally different thing. For instance, stacking 2x24x.1 is not going to be the same as 1x24x.2. The former will be much softer.

 

[marcusgunby]

i think i can assist you- afriend of mine has experiments with a softer HSC stack that uses a 10.25 as the clamping(last)shim and its working really well-give it a try.Also yes many people are amazed when they ride the 125sx for the 1st time-its a rocket with rods as suspension-when its new its even worse.As a comparison my 01 CR has this stack when new
24.1(12)
22.1
20.1
18.1
16.1
14.1
11.1
with 0.43 springs!! and those pesky extra bleed shims(they cover the bleed holes and the bleed circuit has to blow them open to get the oil past.
now you would think they would be unridable for a 165lb rider but i liked them and only after chatting with people did i learn they had a reputation of bieng very stiff.:rolleyes: