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'reading' spark plugs

Discussion in 'XJ Technical Chat' started by darthraider, Jan 19, 2013.

  1. darthraider

    darthraider Member

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    Hi,

    I know spark plugs can tell a lot about the engine and whether it's working as it should. But I just recently started working on my first bike, so I'm still kind of a rookie.
    Anyway, I took a picture of mine while doing a valve adjustment.

    http://i49.tinypic.com/orkktf.jpg

    Can someone tell me what those spark plugs are indicating? Especially #2 and #4 (left-to-right).
     
    darthraider, Jan 19, 2013
    #1
  2. k-moe

    k-moe Pie, Bacon, Bourbon. Moderator Premium Member

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    The lighting isn't good enough for me to tell what's going on #2 and #4. The tan color looks right in the range that you want. Are the dark deposits on #2 and #4 sooty or oily? I notice what looks like oil on the shoulder of the threads of #1 and #2. You may be burning a little oil, but I'm not great at reading plugs that aren't in my hand.
     
    k-moe, Jan 19, 2013
    #2
  3. darthraider

    darthraider Member

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    On the shoulders of #1 and #2, indeed that seems to be oil. The dark stuff on #4 is not oil from what I can tell.
     
    darthraider, Jan 19, 2013
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  4. k-moe

    k-moe Pie, Bacon, Bourbon. Moderator Premium Member

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    OK if #4 is sooty, and not oily, then that carb is set a little too rich. The others look fine, but not great. You could go leaner on all 4, but you don't absolutely need to. The oil on #1 and #2 makes me think that you have a weepy valve cover gasket, since it's on the shoulder of the plug. If the bike is running well you could either leave things as they are, or use a Colortune to dial the carbs in. Before doing anything though I'd get new plugs and go for a ride just to get a better look at the plug color.
     
    k-moe, Jan 19, 2013
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  5. RickCoMatic

    RickCoMatic Well-Known Member

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    They look pretty-good to me.
    4 might be a skooch rich.
    Less than the width of a Dime at the Mixture Screw.

    If you were too ColorTune right now, ... the Color might not be Blue.
    But, it would be where you want to be.

    That Color on your Plugs means your Mixture is safe.
    You have combustion(s) that are "Cool" and won't overheat you.

    If you do a Plug Chop with New Plugs and Kill the Plant at High-revs; the Plugs might look a little Yellow.
    That would be High-speed glazing.
    You would need to add a half-a-dime to all 4.
     
    RickCoMatic, Jan 19, 2013
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