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KTM 690 desert shim stack, help please!

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I have a 2009 KTM 690 with 275mm travel WP CC forks (not stock on this bike, I had forks from a 505 shortened) and 285mm rear travel (stock was 275mm) with linkage suspension. The forks are currently able to handle much more than the shock, so I’m not trying to address them any further right now. After 3 revalves, the rear end is still not where I want it to be. Shock was serviced ~10hrs ago. With the current valving I have the LS comp adjuster run all the way in and the HS comp 1 turn out and it is still not stiff enough so this certainly needs to change. It does work okay in choppy/ rocky terrain, and it does not deflect off of sharp hits, but there just is not enough comp to handle whoops and g-outs. I have the rebound almost all the way out (21 clicks) as I could feel it packing when I had it at 12-16. Having it this loose helped tone down the swapping side to side in the whoops (but it still happens), and it never feels like the back end is kicking up, so I think I have too much rebound.  I am not doing the work on the shock myself, but I would still like some input on changes I should make to my current stack since this is a more obscure application than most shops deal with. I know it's a big bike, but it should still be able to do better!

 

Rider:

6'5"

230lbs

"B" level (or better) offroad rider

 

Rear stats:

spring: 9.5kg/mm

static sag: ~28mm

rider sag: 94-95mm

preload: 17mm

 

stock stack:

 

comp:

 

5) 40x.20

2) 38x.20

1) 36x.20

1) 34x.20

1) 32x.20

1) 30x.20

1) 28x.25

1) 26x.25

1) 19x.30

 

Reb:

 

1) 32x.25

1) 24x.15

2) 32x.25

2) 30x.25

1) 28x.25

1) 26x.25

1) 24x.25

1) 22x.25

1) 20x.30

 

Current stack:

 

Comp:

 

6) 40x.20

2) 38x.20

1) 36x.20

1) 34x.25

1) 32x.25

1) 30x.25

1) 28x.25

1) 26x.25

1) 24x.25

1) 20x.30

 

Reb:

 

2) 32x.25

1) 24x.10

1) 32x.25

1) 30x.25

1) 28x.25

1) 26x.25

1) 24x.25

1) 22x.25

1) 20x.30

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You could go back to std reb cross over but with your 2 face shims as that would reduce the hs rebound a fair bit with the wider cross over gap engaging the hs later

On the comp I would add a 22.25 and change the 38 and 36 to 0.25 and add a couple of face shims ; that should get you close

Edited by mog

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I also think a 10kg rear spring is needed , you should get same numbers with less preload

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With the stiffer rear spring the rebound stack now might work

Edited by mog

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So something along the lines of this?:

 

Comp:

 

8) 40x.20

2) 38x.25

1) 36x.25

1) 34x.25

1) 32x.25

1) 30x.25

1) 28x.25

1) 26x.25

1) 24x.25

1) 22x.25

1) 20x.30

 

Reb:

 

2) 32x.25

1) 24x.15

1) 32x.25

1) 30x.25

1) 28x.25

1) 26x.25

1) 24x.25

1) 22x.25

1) 20x.30

Edited by TheLetterJ

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I also think a 10kg rear spring is needed , you should get same numbers with less preload

 

I had questioned that as well, but when I look on KTM's "shock setting list" it shows 20mm of preload as standard, my 17mm seemed as close as I was going to get to that target. Wouldn't the stiffer spring with less preload give me more static sag, which I already have enough of?

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Thank you for your input Mog, I really do appreciate it! I'll likely send it out with that as a "build to spec" sheet soon. Does anyone else see a different way to skin this cat?

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I mailed my shock out yesterday along with a spec sheet so I am just waiting to hear back from the shop on their opinion. When I called, they said that they generally would recommend valving about 20% stiffer (but at what shaft speed?) if someone was having bottoming issues with the shock... I have no idea how this new stack compares from a percentage standpoint or if 20% is even that big of a change? How big of a difference (in %) is fully open to fully closed typically with just the clickers? Hopefully I'll have it back by the end of next week so I can play with it on the weekend.

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How big of a difference (in %) is fully open to fully closed typically with just the clickers? Hopefully I'll have it back by the end of next week so I can play with it on the weekend.

Probably 10-30% at mid to high shaft speed. At low shaft speeds the difference is much more pronounced, could easily be 2X the damping or more going from open to closed. However, after the shaft speed picks up the differences get much smaller.

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I've been running the shim stack that Mog suggested for almost a year now and I've most definitely spent time focusing on trying to dial it in. I STILL do not have enough low speed comp with my clicker maxed out. I bottom frequently and have to scrub off speed for small kickers and g-outs that even my stock valved GasGas has no issues coping with. Though I can ride through whoops at a somewhat reasonable pace now, there is no way I trust the shock enough to actually charge them. Hi speed comp seems okay if not on the stiff side at 1/2 turn out, but if I back it out to the point that hi speed is best (about 1- 1 1/4 turns), low speed gets softer with it, much too soft.

 

Rebound is working well at 10-14 clicks out depending on the day, so I'm happy there.

 

I'm down ~10lbs from last year but I haven't changed my preload on the rear as I like the way the bike turns, in fact, I wouldn't mind if the rear rode a little higher.

 

Those things being said, will going from a 9.5 rear spring up to a 10 or even 10.5 (which is certainly stiffer than anyone would recommend for me, I'd likely have to run at nearly zero preload) make a large enough difference in bottoming resistance/holding the bike higher in the travel to be noticeable or is another revalve in order?

 

I figure that another service wouldn't hurt at this point, so the time to revalve would be then.

 

What would your (the TT collective's) suggested changes be to my current comp shim stack?

 

Currently:

 

8) 40x.20

2) 38x.25

1) 36x.25

1) 34x.25

1) 32x.25

1) 30x.25

1) 28x.25

1) 26x.25

1) 24x.25

1) 22x.25

1) 20x.30

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It was brought up on another forum that my DCC adjuster stack might be a better place to look for a solution. The problem is that I do not know what stack is currently in there (other than it being the factory stack) and do not want to open the shock up myself being that I'm not really equipped to put it back together! Does anyone know where I might be able to find what the factory shim stack is for the DCC?

 

KTM's shock setting list does not show it:

 

20140121_175416_zpsc508d74b.jpg

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If it were me I'd add more 40.20.....4 or 5 and see if your moving in the right direction.

I had the same issue with a 06 crf 250....the low speed was too soft and almost mushy....I ended up adding more face shims than I expected....after several reshims I hit paydirt and found a stack that suited my liking.

I think your just not going stiff enough.

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The DCC stack should be shown on the shim setting sheet ,have another look ,and it's not a bad idea to stiffen it if you have gone to the point where the main stack is significantly stiffer ,as they are meant to balance each other ,if it has 0.15 shims you can change them to 0.2s

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The DCC stack should be shown on the shim setting sheet ,have another look ,and it's not a bad idea to stiffen it if you have gone to the point where the main stack is significantly stiffer ,as they are meant to balance each other ,if it has 0.15 shims you can change them to 0.2s

 

Here's the FULL page of the KTM setting sheet:

 

20150513_100340_zpsa8b55a0b.jpg

 

I hate to keep relaying info between forums, but it may help with the brainstorming. It has been suggested to just remove the bleed shim and/or crossover (if indeed there is one) from the DCC stack and change my (8)40x.20 face shims on the main piston to (6)40x.25's to stiffen up the main comp stack. That seems like it would be a pretty substantial jump, and might be a good place to start?

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This unusual it's not listed ,normally they are , Terry suggestion is good if you do just that piston ,if you do both pistons then something less stiff would work ,without seeing the adjuster stack we can't comment , they often do use a small face shim but it's not actually a bleed as it does fully cover the port ,personally I think doing both pistons is the best answer and Terrys is the easiest answer ,you dint want a really stiff Midvalve and soft Base valve which is what you may end up with here

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