shim shuffle - KTM WP forks

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#16
Servus James,

Why not go in on the LS clickers?? Yes, the oil has to flow, but the valving shims are there to open for the high speeds.
I don't want to go in farther than 1/3 of the available clicks! Why? I'm of the oppinion that LSC added by shims and LSC added by going in with the clickers is not the same!

Whether you want to add a crossover to the middle of the HS stack or just expand the existing crossover is a matter of preference.
No, I think we are talking about different things here. When you widen the crossover gap, you are influencing the shim stack BEFORE the HSC stack comes into play. I'm talking of altering the HSC stack itself - the effects cannot be the same!

You wanted to make the forks more compliant for rocks and woodsriding, I'm aiming at reducing deflection at high speeds and sharp edges.

Michael
 
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#17
Michael,

Your points are well made when searching for a perfect solution. My comments were made hoping for good discussions.

***Keep in mind those WP forks have 14mm cartridge rods. They push more fluid through the valve and are more sensitive to pressure than a 12mm rod. (36% more fluid compounded with 36% more area on the rod)

-Low speed clickers work in parallel with the LS shims. They overlap within a range. There is a point where I would aggree with your arguement and for me it is more like 1/5 rather than 1/3. This may just be 5 clicks vs. 8 clicks to increase LS-comp and help reduce bottoming. Not an ideal answer though.

-The crossover expansion should be looked at with the 14mm rod in mind. An expanded crossover gap from .15 to .20 will not be nearly as noticeable as on a 12mm rod fork. Also, the effect of reduced stiffness on the HS stack will match the damping of an increased crossover gap WITHOUT reducing the HS stack stiffness at some "uncertain" velocity. My point is to look at tension vs. deflection instead of stiffness alone. The 2 stackings will have similar damping, although to be precise you are correct that it's not exactly the same.

That said, here's my suggestion-

24 x 0.1 2x
15 x 0.1 (a little more support for the 24's)
12 x 0.1 (total gap now = .2)

22 x 0.1
18 x 0.1 (remove the 20 x 0.1)
16 x 0.1
14 x 0.1
12 x 0.1 (this just looks better on paper
)
10 x 0.3

If I were a KTM engineer for a day, the SX would use the current compression valve and the EXC/MXC would get a valve with 40% greater port area. They should have different valves for their intended uses IMHO. Square ledges are HS damping at 20mph just as much as rounded are at 50mph. Gut feeling is this design is never going to be as plush as the Marzocci's of years past.

---------------------------------------
***** The pro's on the forum will disagree, for certain. The party line is generally a soft single stage, maintaining shim seat pressure as best possible on the stock piston and use the port restriction for high speed damping. It works for the 12mm rods, but will it for the 14mm?? It didn't for me 3 years ago so why should it now?


A different suspension tuner was involved and the promise of relief from square edges was never achieved despite their valve mods. I made lots of shim stacking tests along the way too. All the way to mush, and the HSCD harshness was still there.

-------------------------------------

BTW - Christmas was good this year, a '00 KTM 250EXC found it's way into my garage. YAHOO!!

(already had the comp valve apart and it had shims just like yours plus the 12 x .1 in the HS stack)

James

[This message has been edited by James Dean (edited 12-28-2000).]

[This message has been edited by James Dean (edited 12-28-2000).]
 
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#18
Servus James,

Ok, lets see:

24x0.1 2x

At first I though of adding another 24x0.1 shim, but after looking at my Gold Valve chart this seems too radical a change.

15x0.1
12x0.1

You are a good salesman ;-) I would have changed the stock 12x0.15 to a 13 or 14x0.15 to stiffen LSC a little, but your suggestion seems very interesting. Besides, I'm also curious how the enlarged crossover gap works. Sold!

22 x 0.1
18 x 0.1 (remove the 20 x 0.1)
16 x 0.1
14 x 0.1

Nope, I like the 22x0.1, 20x0.1, 19x0.1, 17x0.1, 14x0.1 very much so far, so I won't change it this time. Maybe removing the 20x0.1 from this stack, but that's something for later.

12 x 0.1 (this just looks better on paper
)

I want to go even more radical like 14x0.1 (or 14x0.15), 13x0.1, 12x0.1, 11x0.1 to fight bottoming after large jumps without raising the oil level to its maximum.

So after I receive the shims I've on order my stack will look like this:

24x0.1 2x
15x0.1
12x0.1
22x0.1
20x0.1 (candidate for removing)
19x0.1
17x0.1
14x0.l
13x0.1
12x0.1
11x0.1 (probably useless)

Gut feeling is this design is never going to be as plush as the Marzocci's of years past.
That's one of the problems here - once you have ridden or owned a bike with great suspension, you are spoiled forever. This was with my 1998 Yamaha WRz400 with Gold Valves (valved after a recommandation from MX Tuna - thanks) and an Öhlins shock revalved by MH Racing. This bike worked for me being fast or slow, doing MX or Enduro, just everywhere! I won't stop experimenting with the KTM till the suspension works either as good or I sell the bike!!!

Nevertheless I'm very hopeful because the stock suspension works so well (surprisingly). None of the KTMs I've ridden previously, including my riding buddies 2000 KTM 250EXC after 2 revalves, came even close. Hope you have more luck with yours!

BTW, when the suspension is fixed we can start the "needle-thing" - again ;-))))

Thanks a lot for sharing your ideas and experience - just too bad you can't go for a beer on the internet.

Michael
 
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#19
James, I forgot:

already had the comp valve apart and it had shims just like yours plus the 12 x .1 in the HS stack)
Can you post a picture of the valve? I'd like to see if the 2000 and 2001 valves are identical.

Michael
 
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#20
Michael,

Can't give you a picture right now, the valves are already back together in the bike. The part number in manual is #4860.0047. Does this match yours?

The shim stack was put back together as was suggested except for a bigger crossover -
15x0.1
12X0.15 (total gap now = .25)

Time will tell how good it will perform.

For your perspective: This is a woods bike only. It will see lots of rocks, roots, some whoops, and narrow 2nd/3rd gear trails with the bars skimming bark off the trees. Rarely will it see a jump. I'm considered a to have a smooth riding style and don't bottom out very often. Basically an old fart in good shape. Running 2 marathons every year, last one took 3hrs 12 min.


James
 
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#21
Gentlemen, I have read this topic with a lot of interest. I have a 00 200EXC with the same stack as drehwurm listed with the addition af a 18 x.2shim at the bottom, below the 10mm x.1. My question to drehwurm or james dean is: Have either of you rode the bikes with the mods that were mentioned? I too ride tight trails and I am very interested in how these mods worked. I had coinsidered similar stacks, but your discusion has me reconsidering what I was going to do. I would love to hear your comments.
BTW James your posts on the needle info has been very helpful.
Thanks Tony
 
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#22
Servus tonyr,

I have a 00 200EXC with the same stack as drehwurm listed with the addition af a 18 x.2shim at the bottom, below the 10mm x.1. My question to drehwurm or james dean is: Have either of you rode the bikes with the mods that were mentioned?
I've ridden a 00 200EXC and didn't like the forks at all - same with all the 00 KTM 2-strokes I got a chance to ride. The 00 4-strokes and all the 01 KTMs differ in one (IMHO a critical one) point from your bike: the bleed holes in the cartrige have been enlarged from 7mm to 8,5mm. So even if we have the same shim stack, the forks will work differently. Oil weight and brand is critical also.

James does have a 00 250EXC so his experiences should be more comparable than mine. Besides I'm still waiting on my shims to come. I'll post the results as soon I have them.

The 'shim' on the bottom normally works as a base plate - it should be thicker than 0.2 though. (we are talking mm here!)

Michael



[This message has been edited by drehwurm (edited 01-17-2001).]
 
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#23
On my '01 380sx forks all I have done is replace the soft .41 springs for stiffer .46 and they work great for MX. The faster you ride the better they work.

CP
 
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#24
Hey,

Where are you guys finding the best pricing on shims? I bought some from WER and they were a bit on the pricey side (1.39 ?).

PT