Replacing KTM 640 Adventure head gasket ... guidance?

Discussion in 'Thumpers' started by D0dja, Jan 28, 2013.

  1. D0dja

    D0dja Sandwurm

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    I'm pretty sure the head gasket has gone on my 2002 640 Adventure -- coolant vanishes if I push it hard and get an insta-overheat; also bubbles rising in radiator with cap off.

    Is there a way to check if it's head or base gasket?

    I'm looking at doing the head gasket myself - there's very little info on this topic (unless I missed it in search?). Is it relatively straightforward (have a copy of factory manual) ... what's the chance of warped head? Should I leave this to a workshop?

    I generally work on my bike myself, but not done something this major. I have also had LOTS of really miserable experiences with agents, workshops, etc, so would prefer to do it myself.

    I recently replaced the seals on the water pump shaft and resealed tappet cover, which fixed the one coolant disappearing problem (and mayonnaise in oil) and a oozing oil leak.
    #1
  2. gunnerbuck

    gunnerbuck Island Hopper

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    If a gasket is leaking, it can only be the head gasket, as the base gasket does not seal the water jacket... You can pressure test the system before you remove the head by blocking off the lower rad to block tube and then make an air filler plug to bolt over the thermostat fitting above the spark plug... You can add 50lbs pressure into the block and see if it holds for a while... If it does hold then your leak is outside of the cylinder waterjacket, either at the waterpump, rad or hose fittings...

    If the leak is found within the water jacket then it will either be a faulty gasket or a cracked cylinder/head...


    This thread will give you an idea of how to pressure test: http://www.advrider.com/forums/showthread.php?t=405073
    #2
  3. D0dja

    D0dja Sandwurm

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    Great, thanks for the feedback.

    Will try talk a nearby bike shop into testing it for me (in exchange I'll buy more tyres and a new chain from them :) )

    I recently relocated and now living in an apartment so don't have a workshop to fabricate things. Going to have to strip the engine in the garage at my girlfriend's place. Sigh.

    The alternative is having the local bike shop do it - they have good rep, but I talked to the mech and he has not worked on the 640 much (they mostly do dirtbikes), And I'm a bit anal about how stuff is out together. Prob cost around $200 labour. Hrmmmm.
    #3
  4. D0dja

    D0dja Sandwurm

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    I stripped the head and replaced the gasket. Problem not solved.

    Pulled head off again.

    There's a crack across exhaust ports right down to the valve stem seals. Unfixable,

    I'm not a happy bunny.
    #4
  5. Kawidad

    Kawidad Long timer

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    Ouch! :huh
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  6. Droptarotter

    Droptarotter Long timer

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    Are you sure it's not repariable??

    Have you taken it to a good welder? Some of the welders are amazing what they can do.

    Good luck.
    #6
  7. D0dja

    D0dja Sandwurm

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    I took it to a guy who's apparently very good, does all the repair work for one of the Kawasaki racing teams, has a good rep.

    Recons it's cracked right to the valve stem seals, so can't even get in there.

    Have a lead on a second hand head...
    #7
  8. vilecon

    vilecon Adventurer

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    Hello everybody, I am repairing the entire engine of my KTM 640 Adventure myself and I thank you all at advrider for your help.
    I have a doubt.. do you think I should use silicone on the cylinder gasket and head gasket?
    Look at the picture.[​IMG]
    Regards:
    Jose from the Andes in Peru.
    #8
  9. vilecon

    vilecon Adventurer

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    [​IMG]
    #9
  10. gunnerbuck

    gunnerbuck Island Hopper

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    Do not use any kind of sealant on the head gasket...

    The manual calls for use of a 1211 type sealant just on the narrow part of the base gasket around the cam chain tunnel...
    #10
  11. vilecon

    vilecon Adventurer

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    Thak you very much Gunnerbuck.

    So.. I have to use sealant only on the narrow part of the cylinder gasket?
    The narrow part means all the tunnel or only the narrow inside part? becuse all the outside of the gasket have a indent (notched) so that no oil leak.
    #11
  12. gunnerbuck

    gunnerbuck Island Hopper

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    Just on the outside of the gasket
    #12
  13. vilecon

    vilecon Adventurer

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    Thank you very much!!! Nice country Island... I was living seven years in Norway.
    #13
  14. kveldulv

    kveldulv Adventurer

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    That's interesting. You're saying just in the area I've shaded green?
    [​IMG]
    I had interpreted the service manual instructions ("apply sealant to the sections near the chain tunnel") to literally mean all around (both the green and yellow areas). When I removed mine, the factory installed gasket showed sealant mainly in the yellow area, and little evidence of anything in the green area. I think I still have my old gasket, so I might double-check.
    #14
  15. gunnerbuck

    gunnerbuck Island Hopper

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    The yellow area seals the crankcase from the gearbox so anything that weeps through that area stays within the confines of the engine ... The green area has been a problem area on some bikes from back when they used paper base gaskets... A bit of sealant on the yellow area shouldn't hurt things, but in my mind the green area is of more importance...
    #15
  16. kveldulv

    kveldulv Adventurer

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    Makes sense, though I always thought (read?) that the sealant was as much about helping the gasket stay put (prevent slip/blow out - which also seems like a throw-back to the paper gasket days to me) and in that context, the "yellow" bit looked the most vulnerable to me.

    I haven't done mine yet, so the topic is interesting to me!
    #16
  17. kveldulv

    kveldulv Adventurer

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    For the record, I took another look, and it's not quite what i thought. It seems as though a large(r) amount of sealant was used near the rear stud which squished out along the inner ("yellow") part.
    #17