Help - Valve specs and temperature

Discussion in 'Crazy-Awesome almost Dakar racers (950/990cc)' started by folknride, Dec 11, 2012.

  1. folknride

    folknride Old Adventurer

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    I'm doing a 30,000km valve check on my 2010 990 S here in my chilly garage in chilly Alberta. Specs are for 20C (room temp) and it's probably more like 5C in my garage. All valves are at the low end of spec except one exhaust that is about .03 mm tight. My question is does colder temps reduce or increase gap?
    Should I change shims or leave it 'til next time?
    Thanks for any advice from you good physics guys.
    #1
  2. Black Hills

    Black Hills Long timer

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    Clearance increases at colder temps (the metal contracts). But I have no idea how much.
    #2
  3. dmn0507

    dmn0507 Been here awhile

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    I think the most affected part is the valve stem (since is pretty long)
    With lower temps the gap should be increased, since the stem gets shorter, but i guess the difference it's not that big (let's wait for somebody who wants to do some math :D)
    #3
  4. folknride

    folknride Old Adventurer

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    Thanks - kinda what I thought - but my brain sometimes "malfunctions". I'll pull the shims and shoot for the high end of spec.
    #4
  5. markjenn

    markjenn Long timer

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    Hard to say. I think the big thing with setting a valve "cold" is for the engine not to be recently run - beyond this, the actual temp is probably not a big factor.

    Whether you could let this valve ride is up to you. Nothing bad usually happens when you let one that is slightly out of spec go till the next adjustment. But I don't think you can assume it will be in spec if your garage was 15-deg warmer.

    Personally, I wouldn't make extra work for yourself doing extra valves, shooting for the high end of spec. For one, the shims typically don't come in that fine an increment where you can nudge the clearance precisely to the top end of spec, and second, you may end up overshooting or causing some other issue. Further, valves don't necessarily tighten with wear as everyone thinks - sometimes they can go the other way so moving towards one extreme of spec may just be increasing the risk you're going to have to do it again the next adjustment. Not to mention the extra work and expense, especially if you end up messing around with a head you wouldn't have messed with otherwise. If you just have one valve out, I'd just shim that one.

    - Mark
    #5
  6. folknride

    folknride Old Adventurer

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    Thanks Mark - now I'm kind of torn. Harley shims come in .025 intervals and I could move close to looser end of spec on all valves. KTM - I could just do the one tight exhaust. Folks always say loose valves (within spec of course) are happy valves, and once i've pulled the cams .... Hmmmm?

    Anyone else with advice?
    #6
  7. gozirra

    gozirra Spam?

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    I know this may sound strange, but if you are elbow deep in the job and it is a huge issue, why not heat the garage (I know a waste and time and $$$) just to get the check done within spec.
    #7
  8. Qwik

    Qwik Adrenaline Addict

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    Well, You are already there.....
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  9. uraberg

    uraberg whosaberg?

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    I'm going to say that the temperature difference between room temp, and operating temp makes the 15 degrees difference in your garage insignificant.
    #9
  10. gozirra

    gozirra Spam?

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    68 vs 41 degree fahrenheit, i think he listed celsius.
    #10
  11. RadoR6

    RadoR6 Adventurer

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    If you're not sure how about to put a heater into your garage:wink:?Wondering anyway how someone can do servicing in a cold garage with frozen fingers?
    #11
  12. folknride

    folknride Old Adventurer

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    Thanks guys - I'm just going to do them all - now I'm in it - and the Harley dealer has lots of stock.
    (except I can't get the freaking spark plug tube to move - swearing profusely as indicated)
    #12
  13. folknride

    folknride Old Adventurer

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    Why am I doing this - because I'm a world class procrastinator and need to get ready to leave for sunny Kali!

    Got my longies on and a space heater - and hey - I'm Canadian eh?

    :rofl
    #13
  14. Sporting Wood

    Sporting Wood I

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    Boy, it looks like KTM is coming out with their new 1190 StarCruiser at just the right time. :norton
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  15. Hipster

    Hipster Long timer

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  16. folknride

    folknride Old Adventurer

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    Harley dealer had every size I needed - 36 bucks for 8. Harley parts in my KTM - oh the humanity :norton
    #16
  17. rotarygirder

    rotarygirder Adventurer

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    I'm in the middle of my valve job right now. I tried to call a Harley dealer the other day to get individual shims and their parts department convinced me that valve shims did not exist, and I had to be thinking of valve guides.

    After that conversation I went ahead and bought the Hot Cams shim set. All of the ones I will need measured within .015mm of their spec'd size, most were less than .005mm off. Not bad for $60, especially considering their size divisions are .05mm and now I have enough of these things to take care of both of my KTMs.
    #17
  18. kamanya

    kamanya Andrew to most

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    The Harley guy last time I went in the there said, "you working on a KTM aren't you?"

    "Yep, how'd you know?"

    "No V-Rod guys here do their own valves, you KTM chaps are the only ones who ever buy them over the counter."
    #18
  19. RedRupert

    RedRupert Brit in the Soviet Union

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    Set the valves on the loose side. Get the shims spot-on with the aid of emery cloth:

    [​IMG]
    #19
  20. folknride

    folknride Old Adventurer

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    The Harley shims measure pretty true - just one of the eight is about .01mm thin - so should be good - still within spec.
    On another note, how much carbon deposit are folks seeing on the back of the valves? I've got some uneven (lumpy?) carbon on mine - not a ton but it's there. Everything else is clean after 30,000 km - plugs have normal deposit
    #20