990 Rear shock rebuild - any service documents?

Discussion in 'Crazy-Awesome almost Dakar racers (950/990cc)' started by HellSickle, Dec 28, 2012.

  1. HellSickle

    HellSickle Scone Rider

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    I just changed the oil & recharged my rear shock. As far as the primary innards, it's like any other WP shock.

    However, the hydraulic preload is something I've never messed with. It's a separate circuit and I didn't touch it during the freshening.

    Anyone have a source of documentation for a complete rebuild for these shocks?
    #1
  2. DirtyADV

    DirtyADV Long timer

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    Afraid not, don´t tackle the rear shocks myself and have just told my shock guy to leave the hydraulic preload alone but could be good to have a manual for the day when the preload fails (hopefully far away).

    And since I have ended up with a second set of "suspenders" I wont be stranded when it does but a .pdf on the computer would be great!

    /Johan
    #2
  3. HellSickle

    HellSickle Scone Rider

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    FYI, doing your own shocks isn't a big deal. Given how hard they work, they need fresh oil far more often than they actually get. I've had my own N2 cylinder for years. Bleeding on the WP shocks was made much easier with a homemade vacuum bleeder. Someday I'll post up details on this engineering masterpiece. :wink:

    Shock is now done. I didn't touch the preload adjuster. I'll dig around the net for shock manuals to see what I can find.

    BTW, anyone with a 990 service manual they might be willing to share? I've got one for the 950, but would like to get something closer to my bike.
    #3
  4. HellsAlien

    HellsAlien a has-been that never-was

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    I found that routine riding ('ya know: baja, magruder corridor, etc) builds up dirt and dust on the ID/OD of the big end of the adjustor. I just clean that out so the big O-ring seals there don't grind on the accumulated dirt. I've never had to add oil or rebuild it ('05 bike.)

    Prolly shouldn't say that.. last time it was slave cylinder seal gave out in baja back-boonies. :evil

    Oh yeah, vacuum bleed is the only way to go. Even a small hand bleeder will pull up to 28 inches Hg. And anybody with a decent wire welder has argon bottle on board to charge a shock; but 'ya might have to fiddle with the regulator to get enough psi to the shock.
    #4
  5. HellSickle

    HellSickle Scone Rider

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    Rear suspension has a fraction of the oil of front suspension and has a lot more heat to deal with. Try putting a hand on a shock after riding in a very rocky section. It can get too hot to touch. All that heat leads to break down of the oil and wear of the shock components.

    I built my vacuum bleeder out of a bunch of PVC. The vacuum source is a venturi vacuum from Harbor freight (used to vacuum out automotive AC systems). I alternate filling the shock with low pressure oil to oil under vacuum. The whole thing runs on compressed air, so all I need to do is flip various valves to thoroughly flush all of the air out of the system. About 8-10 cycles eliminates all of the bubbles.

    Since I didn't want to convert all of my bikes to Schrader valves, I machined some fitting to allow an N2 cup with sealed allen wrench access to the pressure screw. A big C-clamp holds the works in place.
    #5
  6. Brokein2

    Brokein2 Been here awhile

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    I remember seeing your vacuum bleeder on KTMTalk a few years ago......definitely a cool tool. :freaky

    Next Spodefest we will have to have a big bikes ride with you, me, and Eric.
    #6
  7. DirtyADV

    DirtyADV Long timer

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    A good detailed guide for going over the rear shock would be welcome will probably start looking into doing oil changes myself but learning step by step and have started to tackle the front end myself for now.

    /Johan
    #7
  8. ÖÖ.

    ÖÖ. Ajaa kuin mummo

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  9. HellSickle

    HellSickle Scone Rider

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    Thanks, but it doesn't cover the shock with the hydraulic preload adjustment.

    Even the KTM parts fiche doesn't show any detail of the preload adjustment. Apparently, you are supposed to buy an all new upper shock body for $900+ if a seal goes out.
    #9