weeping lower cylinder gasket - retorque to higher Nm?

Discussion in 'Crazy-Awesome almost Dakar racers (950/990cc)' started by fast4d, Apr 8, 2017.

  1. fast4d

    fast4d Long timer

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    I've got a slight leak on the rear of front cylinder. at the base of the cylinder (not Head gasket).

    I've verified it is not the oil sensor nor starter o-ring.

    I recall reading someone remove one head nut at a time. lubed with motor oil. torqued to 25nm. repeat the other three nuts. then torque to 38Nm (factory spec) .....then to 43NM (over spec).

    worth while or ?
    #1
  2. wiseblood

    wiseblood Not Your Safe Space

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    Couldn't hurt to make sure they're tightened to spec.
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    zedtours likes this.
  3. COXR650L

    COXR650L Long timer

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    I doubt it works. Im pretty sure someone (Pydon?) here documented how the two metal surfaces end up pitting each other, resulting in an oil leak. When I did my engine rebuild there was evidence of this. I think the correct fix would be to pull the jugs and use a good sealant, like Ultra Grey Silicone, between the jug and case with a new base gasket.
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  4. uk_mouse

    uk_mouse Aquatic adventurer

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    Pretty sure the fault Pyndon described was on older engines, and OP's sig says he has a 2013, so quite possibly not applicable.

    Retorquing the head nuts can't hurt - in the past I have had success in stopping a leaky head gasket that way. FWIW older workshop manuals gave the head nut torque as 43Nm, and it was changed to 38 later (possibly with the release of the 990 engine?).
    #4
  5. fast4d

    fast4d Long timer

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    I read that post. that is a 950.

    mine is the last year of 990 production. from what I've read on the superduke forums this leakage is quite common. no one mentioned any problems with the sealing surfaces.

    mine only weeps if I ride her in anger. I will retorque and wait till the next valve check/adjustment to replace all the studs/hardware.

    I put alot of miles on her so it will be time again way before end of year.
    #5
  6. RedRupert

    RedRupert Brit in the Soviet Union

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    This problem can occur on all first generation LC8s 950 and 990. My 2004 950 was OK (90,000 km). My 2008 990 started leaking at around 60,000 km, and the damage I found to the crank case was alarming. Last month my dealer had a 2010 with badly worn crank case and distorted barrel that was dealt with under warranty.

    KTM originally (2004) specified 46 Nm for the cylinder nuts. I don't know why they decided to reduce the cylinder head torque later on. I don't think you'll gain much by replacing the studs.

    I filled the trench in the crank case with high temp (190 C), high compression strength Loctite 3479 that is said to be stronger than aluminium, because the trench was too deep (guess 0.3mm) for Hylomar alone. Upon assembly I applied a very thin layer of diluted Hylomar to all surfaces (crank case, both sides of the new base gasket and the barrel).

    I'm really disappointed by this, as these LC8 engines have otherwise proved to be extremely robust (not to mention great fun!), providing maintained correctly.

    My 2008 990 with around 60,000 km.

    20170317_201830.jpg
    #6