LC4 shock rebuild parts?

Discussion in 'Thumpers' started by rz35027, Dec 20, 2010.

  1. rz35027

    rz35027 Been here awhile

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    I have blown the seal on my shock... oil on the bumper and it thunks pretty good coming up on full extension... 620 RXC

    I would like to rebuild this myself and need to know what are the wear parts in an LC4 shock absorber... I know it's not the same as a PDS shock.

    How much of this can be done without any special tools(?) besides the filling with nitrogen? The bleeding can be done... with care taken, by hand. Disassembly should be OK, reassembly should be OK, or, are there tools needed for the shaft seal?

    I have a spare shock (with lots of hours) and an Adventure shock that I'd like to lengthen (take a spacer out) that will also need attention.

    Can someone chime in with some advice pls?
    #1
  2. airgord

    airgord What am I doing out here!

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    Is there anything on the LC4 thread? (bump)
    #2
  3. col klink

    col klink the str8n'r

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    RZ35027,
    I have drawers full of special tools for all the different shocks and forks I do.
    The lc4 shock is not that different compared to the pds shock other than only using one piston on the shaft rather than two.
    I would think you'll probably need a shaft holder (14mm I believe) and a 14mm seal bullet tool to protect the new seal upon installing it.
    I can't think of any thing else you have to have. obviously 150 or so psi nitrogen pressure.
    While you are there you should consider a Racetech Goldvalve kit to make your shock that much better than oem.
    PM me if you like.
    good luck
    #3
  4. laramie LC4

    laramie LC4 crash test dummy!

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    yup, the gold valve is a HUGE improvement over the stock valving. well worth the money if you have the shock already apart.

    laramie :beer
    #4
  5. Luke

    Luke GPoET&P

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    If you don't want to buy a shaft seal tool, just chamfer the shaft with some fine sandpaper and put the seal head parts on the shaft individually, then re-assemble the head on the shaft. There's no need for a shaft holder unless you're disassembling the clevis end, which shouldn't be necessary.

    You will need something to hold the shock body and the reservoir body, and a really good pin wrench. The caps are on really tight. Installing a schraeder valve in the reservoir cap makes recharging the gas easier.

    In addition to the shaft seal, you may need a reservoir piston seal, a shaft bushing and a piston bushing. The parts are the same on the older and newer shocks, so you can use the exploded diagrams on the newer mode parts fiche to see what you're getting into.

    I'm happy with the stock valves, but did change the shims. For me, the stock valving from the '97 adv is way better than the newer ones with the shorter travel. The valving I settled on for my bike is pretty similar to the stock '97. The biggest differences are to account for extra weight and a heavier spring. I'd at least change the newer shock valving to match the older one. Obviously, your valving preference depends on how and where you ride.

    Also, if you lengthen an Adventure shock, you'll need to use the taller spring collar from the 620 so that the spring doesn't hit the engine case at full extension. IIRC, to get the exact length of the longer shock you need to replace the 10mm spacer with a 2mm one. It's not just removing a spacer.
    #5
  6. Tseta

    Tseta Lost

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    Another good and informative thread about the LC4 shock.

    I'm a bit confused about the different wearing parts, that might need replacement.

    I tried to take a look at the fiche (click here), but I think there is a terminology disconnect here. KTM's names for these parts are confusing me.

    I assume that the reservoir piston seals are numbers 87 and 88 on the diagram, parts 46811043 O-RING VITON 35X5 and 46810324 PISTON RING 3,9X1,5X138, correct?

    For the shaft, the shock manual mention a dust seal. It must be number 24 on the fiche, part 46811044 DUST SEAL 1424, right?

    The only other part that I see in the fiche that would be relevant is number 26, part 46811540S1 ADAPTER CPL. D=46, H=23 BA. What is this called, in layman's terms?

    Where do all these parts stand in relation to what Luke listed? Which ones are the bushings, I couldn't find them on the fiche? Any other parts that I missed?

    Cheers,

    Tseta
    #6
  7. rz35027

    rz35027 Been here awhile

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    Good question on the translation of part numbers and laymans terms..
    Can anybody help us out?
    There is some good info in the LC4 thread... and some more developing here... thanks guys
    #7
  8. Luke

    Luke GPoET&P

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    Doh!, terminology.....

    The shaft seal and the shaft bushing are not available separately from KTM. You can either buy a new part #26 for $105, or go to Mcmaster.com and buy them separately. They are part numbers 6679K18 and 90025K228. The bushing is soft and a bit tricky to get in and out so get a spare or two.

    The piston bushing is #77, the reservoir seal is #87
    #8
  9. rz35027

    rz35027 Been here awhile

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    Thank you sir!
    Are these parts equivalent quality (?)... from the prices that's a HUGE difference. $3.08 - bushing, $11.96 (100 pcs) seal... wow.
    #9
  10. Luke

    Luke GPoET&P

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    The bushing looked the same- it's soft steel with a teflon coating. The seal looked like it was a tiny bit larger then the OEM- but the OEM was squashed, hardened and cracked so I can't be sure.

    I put a couple of years and 15k miles on those parts; they never leaked and looked good when I did a rebuild.
    #10
  11. rz35027

    rz35027 Been here awhile

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    I was bracing myself for a big hit with 3 shocks on the table... that's going to help alot!


    Do you have recommended brand of fluid?
    #11
  12. Luke

    Luke GPoET&P

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    I like silkolene rsf pro 2.5wt. Brand is probably not so important. Weight is.
    #12
  13. rz35027

    rz35027 Been here awhile

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    xlnt...
    #13
  14. Tseta

    Tseta Lost

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    Thanks Luke for the explanations and the alternative part sources. I had a look on the McMaster site for the part numbers and did some research, to make it easier to obtain these parts, especially for those of us not in the US.

    It seems that the shock shaft bushing is in fact just a "quite" standard 14mm plain bushing. This type of bushing could be obtained from, for example, INA ( click here). The bushing measures 14mm i.d., 16mm o.d. and 12mm in width. These bushings may be available with either steel or bronze backings, but as Luke said, the steel version should probably be used.

    The shaft seal looks to be a quad-ring (an "o-ring" with an cross-section in the shape of an x). Converting the inch sizes to mm sizes results (at least close enough) in a 13,95mm X 2,62mm "standard size" quad ring. Buna-N material is equivalent with regular NBR.

    -------

    I have some further questions as well. The WP shock manual is slightly vague at best. I hope someone can shed some light onto these issues.

    Is it necessary to calibrate the new bushing with the calibrating mandrel when replacing it? Interestingly, KTM supplies these shaft seal parts as "one piece", but the service, according to the manual, still requires fidgeting with the individual components.

    How about the reservoir piston, then? Is it necessary to unscrew the reservoir body from the shock casting (using the special tool) to gain access to the reservoir piston? Why couldn't one just unscrew the reservoir cap and take the piston out from that side? This way, one could leave the reservoir body in place and so many special tools wouldn't be needed to service the shock.

    Cheers,

    Tseta
    #14
  15. dentvet

    dentvet Long timer

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    who sells a good adjustable pin wrench?

    i have a nitrogen cylinder and regulator, what else do i need for recharging operations?

    i have a vacuum pump collecting dust, what's it good for?
    #15
  16. rz35027

    rz35027 Been here awhile

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  17. Tseta

    Tseta Lost

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    (Bump for the shock service questions on the previous page...)

    Here's another good link regarding the LC4 rear shock. This discusses shock shimming. Probably a bit more advanced than just simple servicing, but very interesting nonetheless.

    Click here.


    -T
    #17
  18. Luke

    Luke GPoET&P

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    Those are the right parts. The O-ring I mentioned is a standard size. It's an AS568A-113 AS568A is the series, 113 is the size.

    You don't necessarily need the special tools to unscrew the reservoir caps but you need some way to hold the body because they are on tight. After you get the cap unscrewed the first time you probably won't need the tool again, unless you loctite it like they do from the factory. I made a clamp on a mill, but if you don't have a mill you could probably rough one out with a saw and then mould some JB weld to get the size just right.


    I made a pin wrench because the one I bought wasn't strong enough. I haven't tried this, but the best DIY design I've heard of is a big Crescent wrench (adjustable open-end wrench) with a couple of holes drilled in it and hardened steel pins pressed in to the holes.

    For recharging, you either need the special WP charging attachement or convert the shock to a schraeder valve. You can use the vacuum pump to help bleed the shock. It's not necessary, but it's easier to get a good bleed if you have one.
    #18
  19. rz35027

    rz35027 Been here awhile

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    "I made a pin wrench because the one I bought wasn't strong enough. I haven't tried this, but the best DIY design I've heard of is a big Crescent wrench (adjustable open-end wrench) with a couple of holes drilled in it and hardened steel pins pressed in to the holes. "

    That's what I built. 12 in Crescent wrench (10 in wasn't big enough for resevoir body) drilled with 11/64 holes, drill shanks cut off and epoxied in... Buy some cobalt drill bits... the wrench body is hard stuff, you may toast a few bits doing this.

    The shock body has the 11/64 holes, the resevoir body holes are larger and farther apart.

    I used a 30 in x 6 in x 3/4 in piece of nylon (plastic) (it could be plywood) with holes (cut with a holesaw) (about 1/2 in apart) for the shock body and resevoir, to use as a means of holding the shock while opening both parts instead of just reefing on the head of the shock in a vice.

    Those things are on tight! It took quite a bit of heat (hot to touch) and two of us to get the shock body apart.

    Good question on the bushing mandrel...

    Now for some kind of bleed system...
    Is it possible to do this without a vacuum pump? Just take more time and patience to get it?
    #19
  20. Tseta

    Tseta Lost

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    I got some 14mm plain bearing bushings. I had an old "adapter cpl" that had been changed by the shop at a previous shock service. I was able to easily disassemble the "adapter cpl" and press out the old bushing, as well as pressing the new bushing in, using just regular sockets and a vice. The calibrating mandrel is and the necessity of it's use is still a big question mark in my book. It is not too expensive, though:

    Part Number: T149
    Description: CALIB. MAIN BUSHING D=14
    Retail: $30.77

    I've been trying to source some quality pin wrenches to take the shock body and the reservoir caps off. This part is clear and obvious, the caps must come off for the shock service. The unclear part is whether or not the actual reservoir body needs to be unscrewed from the shock casting during servicing. The WP manual is really vague on this part. Is it possible (feasible, recommended) to take out the separation piston if the reservoir body is not unscrewed?

    Cheers,

    Tseta
    #20