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plugs not uniformly colored

Discussion in 'XJ Technical Chat' started by tresch, Apr 18, 2012.

  1. tresch

    tresch Member

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    Hey guys! I've posted on here a few times about some weird tuning issues on my bike. In this post I want to cover one particular thing that has always made me curious.

    Everyone talks about the color of the sparkplugs and how that reflects the A/F ratio. I've always assumed that the part we're looking at is the white insulator around the central electrode, and how it changes color.

    On my spark plugs, I never have an even color on that white insulator. One side is always white and the other side is colored lighter or darker relative to lean/rich condition.

    I've attached a visual aid! Is this normal?
     

    Attached Files:

    tresch, Apr 18, 2012
    #1
  2. fintip

    fintip Member

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    Re: plus not uniformly colored

    Seriously? That's your visual aid?

    I mean, I guess it works. Mine actually look just like that. But I was sure this was a sarcastic post at first glance of the picture. Now I'm just not sure.

    No camera? I would have at least hunted google images for a similar plug, I guess.
     
    fintip, Apr 18, 2012
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  3. bigfitz52

    bigfitz52 Well-Known Member Premium Member

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    Re: plus not uniformly colored

    First we need to know which bike (to know what size plug) then I'll explain further when I have a minute to do a whole bunch of typing.
     
    bigfitz52, Apr 18, 2012
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  4. tresch

    tresch Member

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    Re: plus not uniformly colored

    yeah that's the visual aid XD

    I've been riding the XJ650 cross country and I'm 1,100 miles away from home, staying at a friend's place at the moment. Just thinking and felt like asking, but don't have all my tools handy!

    It's a 1982 XJ650RJ Seca, by the way.

    It runs pretty good, but I'm still having some issues. Was just curious if this was normal for the plugs.
     
    tresch, Apr 18, 2012
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  5. TIMEtoRIDE

    TIMEtoRIDE Active Member

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    The radiant heat from the exhaust valve is enough to help "burn" one side of the plug more (clean) than the intake side, which "showers" the plug with a mist of cold gasoline on the darker side.

    It's a small effect, but enough to have a difference in color.

    +1 on real pics :lol:
     
    TIMEtoRIDE, Apr 18, 2012
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