Ever wonder what is inside your 640 shock?

Discussion in 'Thumpers' started by Zerodog, Jan 14, 2008.

  1. Zerodog

    Zerodog Long timer

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    Now you know!! Here is the inside of my shock. I needed to put a new seal in and I decided to try out some different valve stacks. I have some ideas......they could be good.....or could totally suck and I will be doing this again shortly.

    All of the washer looking things are the shims that control the oil flow. These items are arranged in the shock when it is revalved. The thing on the left with the holes is the piston body. The piston separates the compression side from the rebound side. It also controls oil flow to the shims.

    [​IMG]

    The LC4 shock is totally different than the standard PDS style shock in any other KTM. The PDS shocks have 2 pistons a needle and about twice the amount of shims. I will have to post one of those next time I get one apart.
    #1
  2. durtrider

    durtrider adventure sow

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    Yo Dawg! Your gonna get mine to tear apart into littlebitty pieces in about 3 or 4 days! Its boxed up and ready to ship mon-yawna.
    #2
  3. Dotbond

    Dotbond Africa, Africa

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    If you weren't so far away i would send my shock to you.
    #3
  4. Tuff Tunica

    Tuff Tunica Moto-Skiveez creator

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    What the? An LC4 suspension expert right here in SLC? I live in Park City and have had the shock for my 625 SXC sitting at Palo Verde suspension since before X-mas. Still no word. Had I known I'd have brought it to you. Where are you located and I guess I should ask do you do this kind of thing for others? I'm guessing from post #2 that you do.
    #4
  5. Zerodog

    Zerodog Long timer

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    Yes I work on shocks and forks. I specialize in Lc4s because I am one of the few tuners that ride one all the time. So I know what the bike does under the usual riding conditions. It sure as hell isn't MX or serious desert racing. Most guys want a focus on dirtroads and easy trails.

    I do other suspension stuff for other KTMs too, with a focus on trail and desert riding.
    #5
  6. bmwktmbill

    bmwktmbill Traveler

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    Z-dog,
    Another KTM mystery unveiled.
    Thanks,
    b.
    #6
  7. Mtncrzr

    Mtncrzr Just Kidding, not really

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    Hey, mine looks like that; only all together:lol3...

    You can leave most of that stuff out, it only adds weight.

    Which one is the spacer that is added to the Adventure shock to limit travel?
    #7
  8. Yooper_Bob

    Yooper_Bob Long timer

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    I could easily pull mine apart....getting it all back to together, however :huh
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  9. Loadedagain

    Loadedagain making chips

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    yabbut... can you get it all back inside the tube it cam out of?
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  10. Luke

    Luke GPoET&P

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    Interesting. I'll have mine apart after my new spring arrives. So I was wondering why the rebound shims were so much smaller- guess the inner ports on the valve are the rebound and the big outer ones the compression.
    #10
  11. Zerodog

    Zerodog Long timer

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    The spacer is the brown thing on the left under the piston. It is about .5" thick.
    #11
  12. Mtncrzr

    Mtncrzr Just Kidding, not really

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    Zerodog, thank you.

    Are you going to put a bladder in the new shock or stay with the piston?
    #12
  13. Zerodog

    Zerodog Long timer

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    No bladders, bladders are for pussies! :roflI like the pistons. They last forever, work very well and I find they are easier to deal with. I have a vacuum bleed system for doing KTM shocks.
    #13
  14. Hipster

    Hipster Long timer

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    Zerodog,

    Is it pretty much trial and error with various shim stracks until the you hit upon the charactestics your looking for? When you have a shock/ fork revalved are they just altering (adding or subtracting) to the shim stack?
    #14
  15. Zerodog

    Zerodog Long timer

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    It is and isn't trial and error with the valve stacks. You know what the problems are you are trying to fix. So you address those areas with certain configurations of shims. Different arrangements give different effects. But getting just the right set up is trial and error part. That is why testing on the bike is the best.

    Yes for the most part revalving is changing the valve stacks. Sometimes it can also involve changing the pistons too. But revalving is the general term.
    #15
  16. deliminator

    deliminator n00b

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    I've seen warnings in various places about trying to disassemble a shock yourself, something to do with high pressures?

    I'm not planning to take my shock apart but I'm curious what the danger is and what a pro like you does on disassembly to mitigate it.

    I think there is a suspension guy in me trying to get out, I should probably do something about that :D
    #16
  17. Zerodog

    Zerodog Long timer

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    The high pressure inside is 150psi of nitrogen. It should be isolated to your reservoir but that is not always the case. You just let it out. Sometimes though there can be pressure in the shock and oil can squirt out. Learning to work on suspension is cool but it is a test of patience and you need to be willing to improvise and spend some $$ on tools you need to do it right. The oil showers are priceless......:thumb
    #17
  18. Luke

    Luke GPoET&P

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    Well, I'm just an amateur, so I just follow the manual. WP has good step-by-step instructions for both the forks and shocks.
    The nitrogen reservoir is usually charged up to 150psi, so you need to relieve that pressure first before undoing anything else. On some bikes, you just push open a schraeder valve, but the WP shocks use a plain hex screw. I'll be wearing safety glasses when I loosen that screw.

    I haven't heard of anyone getting hurt, but someone did ruin a reservoir bladder by not bleeding off all the pressure first.


    For some good suspension info go over to thumpertalk and ktmtalk. For the LC4, ktmtalk has loads of fork info as most of the ktms use the same forks. For shock info there's nothing specifically for the LC4, but I got some ideas reading discussions about Japanese bikes on thumpertalk.
    #18
  19. Luke

    Luke GPoET&P

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    :wave Unbaptized right here. :knocks on table
    #19
  20. bmwktmbill

    bmwktmbill Traveler

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    #20