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  1. #1
    FIRED!!! JP's Avatar
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    I need some spark-plug analysis:

    OK Folks,
    In February, I had MID LIFE CRISIS 2 out in Florida (for all of 45 minutes)and there was a miss at WOT. It was suggested to change out the plugs (Original plugs with approx 45 hours on the OEM ECU and 5 hours on the Rotax)

    I ordered a set of Denso Iridium IXU27 plugs today, but figured that I should have a set of regular NGKs around just in case.

    1. What is the GAP supposed to be for the NGK's and is the Denso GAP gonna be the same?

    2. I've included pictures for everyone's viewing enjoyment of the old plugs, what do you think? I'm wondering about the brown around the ceremics, and the fact that the one electrode on the left doesn't look quite the same as the others?

    Thanks,
    JP
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    Last edited by JP; 03-24-2007 at 07:00 PM.


  2. #2
    cyoungesq's Avatar
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    This from DENSO Spark Plugs' web site. (www.globaldenso.com/PLUG/basic_knowledge/troubleshooting/index.html )

    Case 4
    · Trouble other than with the engine




    [Appearance]
    Brown deposits on the insulator directly above the housing
    [Results]
    No impact on the spark plug performance
    [Cause]
    This occurs due to electrical stress in the air near the insulator. (This is not a spark plug gas leak, for which it is sometimes mistaken.)


  3. #3
    cyoungesq's Avatar
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    NGK's explaination . . .

    NGK says this about the stain on the plug ceramic... I just did mine, and they had the same stain.







    Is a stain between the insulator and metal shell caused by gas leakage?
    It is not a stain caused by gas leakage but by corona discharge (corona stain).


    When a spark plug is removed, a brownish stain that looks like a sign of combustion gas flow is often seen at the caulked portion of the metal shell.
    This stain is the result of oil particles suspended in air adhering to the surface of the insulator due to the high voltage. It does not affect spark plug performance.
    Corona stain
    Mechanism of corona discharge
    The high voltage applied to the spark gap is also applied to the area between the center electrode and the metal shell, causing an insulation breakdown of the air at the gap (a) between the insulator and the metal shell. The phenomenon is called a corona discharge. The generated corona discharge develops toward the terminal nut. This last process is the pale blue corona discharge that may be observed in dark conditions.

    Corona discharge


  4. #4
    Moderator The Bandit's Avatar
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    Six pack of Coronas, and I will discharge quite a bit.

    JP, The densos dont need gapping, just pop em in.

  5. #5
    Ditto on RXPSteve...

    you don`t need to touch the ND`s unless they were dropped and smashed the electrode, then I prolly wouldn`t use that one anyways!...PR...

    now on the regular plugs you`ll see a decal placard on the ski, usually up front where the front of the seat hides the hull. you`ll see plug number and gap...

  6. #6
    FIRED!!! JP's Avatar
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    Quote Originally Posted by Pale Rider View Post
    now on the regular plugs you`ll see a decal placard on the ski, usually up front where the front of the seat hides the hull. you`ll see plug number and gap...
    ummm, slight problem here:
    MID LIFE CRISIS 2 has been painted, no decal/placards...
    JP

  7. #7
    I usually spray a little brake cleaner (dries fast) and wipe them up a bit. Usually cleans them up....

  8. #8
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    I bet ya that Corona stain comes out with a little bit of lime juice...

  9. #9
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    Quote Originally Posted by jtpmedic View Post
    OK Folks,
    In February, I had MID LIFE CRISIS 2 out in Florida (for all of 45 minutes)and there was a miss at WOT. It was suggested to change out the plugs (Original plugs with approx 45 hours on the OEM ECU and 5 hours on the Rotax)

    I ordered a set of Denso Iridium IXU27 plugs today, but figured that I should have a set of regular NGKs around just in case.

    1. What is the GAP supposed to be for the NGK's and is the Denso GAP gonna be the same?

    2. I've included pictures for everyone's viewing enjoyment of the old plugs, what do you think? I'm wondering about the brown around the ceremics, and the fact that the one electrode on the left doesn't look quite the same as the others?

    Thanks,
    JP
    Left plug a little leaner than the others, might be the missing you were having...which plugs would be considered the front/middle/rear?

  10. #10
    FIRED!!! JP's Avatar
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    Quote Originally Posted by Danny View Post
    Left plug a little leaner than the others, might be the missing you were having...which plugs would be considered the front/middle/rear?
    Yeah, I knew this was coming...
    I did try (honest) to keep them straight,but failed and screwed them up right before the picture. I believe it's the front one...
    JP

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