Rebuilding an Öhlins Shock

Discussion in 'The Garage' started by Donkey Hotey, May 26, 2007.

  1. Donkey Hotey

    Donkey Hotey De Jo Momma

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    Hello almighty doGs of the garage. Today I find myself tearing into a 1986 Öhlins shock that came original equipment on my 650 Cagiva Elefant.

    The bike's history is that it has 5,400 miles and was stored indoors and not running since 1994. Against the nitrogen pressure, the shock eventually surrendered its oily contents.

    As such, there is little internal wear and it basically needs a replacement seal (or maybe not) and new oil. I would imagine that most Öhlins shocks are similar so I'm hoping somebody who has rebuilt one can help me.

    The spring came off, there is a dust cap without a seal that resides around the shaft. I pried that loose. That exposed a dust seal and a machined aluminum collar held in by a circlip. After draining the nitrogen (yes it still had a charge--I was surpised too) I was able to push this seal and collar down into the body and remove the circlip.

    With that the shaft and the internals slid out of the body. There was a nut on the end of the shaft. I removed it and the valving stack. That's where I get stuck.

    There is a large diameter steel collar that looks pressed onto the shaft. I thought the seal came off from the opposite end from the eye but now I'm not so sure. Obviously the eye-end of the shaft has the damping clicker. I'm not sure how that whole affair comes apart.

    Being a holiday weekend I may just try cleaning everything really well and putting it back together with the old seal.

    What I would like to know is: how do I remove the seal from the shaft at this point? Anybody with prior Öhlins experience?

    Thanks,
    Greg
    #1
  2. valvecrusher

    valvecrusher tractus pro pensio™

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    I've done ohlins rear shocks on a yamaha and also an old can-am.

    It seems i had this trouble too.

    I just can't remember what i had to do.

    If I could only see it in front of me........


    Any pics?
    #2
  3. Donkey Hotey

    Donkey Hotey De Jo Momma

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    I stopped by the local KTM dealer for shock oil. The guy there knew exactly what I was talking about. He said the part in the way is the 'topping plate' (yeah, that's what it does) and said that it supposedly just taps off. I'll see in a few minutes.

    I'm going to risk $20 worth of shock oil to see if I can salvage this seal so it doesn't have to wait for parts.

    Getting a hypodermic needle to pressurize the thing could prove to be more difficult than anything else. I have no nitrogen so I'm going to go with really clean, dry, compressed air for right now.
    #3
  4. autogiro

    autogiro Been here awhile

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    FFIW...
    You are close to PPS Racing, Anaheim I recall, I had a set of shocks sent to Stig for a rebuild. Prices are reasonable, he knows the tricks and he has all the right parts.
    Auto:clap
    #4
  5. Donkey Hotey

    Donkey Hotey De Jo Momma

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    The topping plate gets tapped toward the eye of the shaft. That exposes a snap-ring. Remove the snap-ring, slide the topping plate down the shaft and the rest comes right off.

    The seal still looks really good. Now I need to get the large end off the body so I can access the bleed-port in the nitrogen piston. Off to Wally World for some stainless bowls and a turkey baster. It looks like this will be done tonight.

    As an aside: when you get them apart you get to see how nicely these Öhlins shocks are built. The internals all appear to be machined billet--even the nitrogen piston which sees very little load. It's easy to see why they cost so much. Ya' get what ya' pay for.

    Aside #2: there is a nylon shim that limits the amount of shock extension (and therefore--total travel). The Elefants were raced in Dakar on very 'stock' looking chassis. I suspect that removing that shim just might extend the shock (and the total travel) into the 10-11" region. The spring has ample adjustment range and the shim is only about 0.5" thick. I'm sure the spring is far from coil-binding and could easily handle it.

    Hmmm...I wonder if the Marzocchis up front have a similar 'feature' built into them. :evil
    #5
  6. Donkey Hotey

    Donkey Hotey De Jo Momma

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    I'm going to try to buy a new seal tomorrow at the local KTM dealer. The inside of this Öhlins looks identical to the WP on my ATK. In fact, I'd be amazed if I found out that the components weren't made in the same machines. Seriously--they're identical.

    Anyway, this shock does not have an external resevoir. I assume that to bleed the oil I need to take the outer tube off of the large eye, giving me access to the underside of the nitrogen piston after assembly. The nitrogen piston has a small threaded access hole and I assume that I bleed and fill through this hole.

    Have I got this right? Is that the process? Is there some other way to bleed it? I can't seem to get the tube out of the large eye of the shock. Yes, I loosened the locking collar but I just can't seem to grip the tube hard enough to get it loose. In fact, I fear that I may have tweaked the upper portion of the tube (outside the travel range but still!).

    My next step is to spin a bushing on the lathe that just fits inside the tube, then clamp it in the 6-jaw chuck before really tweaking on it. I'm assuming that the tube has to come off to bleed it properly. HELP!
    #6
  7. Donkey Hotey

    Donkey Hotey De Jo Momma

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    HELP! Anybody? :ear

    I can not get the lower tube off of the eye of the shock. I just spent 4 hours making a precision machined clamp to hold the shock tube and the eye still won't unscrew.

    Am I mistaken in thinking that I need to remove that to bleed the oil side of the shock? This shock has no reservoir. It has a floating piston with a threaded fastener in the center that I assume is for bleeding. I can't get to that without removing the eye of the shock.

    My next step is to cut off the shock tube, bore the remainder out of the eye and order a new shock tube. I sure hate to go that route but it ain't lookin' good.
    #7
  8. HellSickle

    HellSickle Scone Rider

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    I've got the needle if anyone wants one ($5 + shipping).

    For my Ohlins, I drilled out the little rubber diaphragm & installed a shrader valve (sealed with JB-Weld). Much easier to pressurize when you don't need the needle & associated valving.

    -Jeff-
    #8