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Thread: How do I know if my bike is properly tuned?

  1. #1

    Default How do I know if my bike is properly tuned?

    Check the color of your spark plugs.

    White / light tan = Too lean. You need to remove discs.

    Coffee with light cream = Just right.

    Dark = Too rich. You need to add discs.
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  2. #2
    Join Date
    Aug 2008
    Blackfoot, ID

    Default According to NGK...

    Spark plug color reading - NGK.

    May I offer my interpretation on this subject? The coloring diagram above is a simple 'do this and not that.' While it is mostly true, I like what NGK had to say about where insulator carbon should be found. Color reading only the insulator tip is incorrect according to NGK. It's the insulator base deep inside that should be checked. If it is white at it's base, the air-to-fuel ratio is too lean. Tan/cream/black at its base is ideal so long as the insulator tip is white.

    Discoloration at the insulator tip is indicative of a rich mixture, probably ideal for short term racing and high performance applications. If the carbon builds up on the insulator tip it will eventually lead to plug fouling (aka dry fouling), where the spark will ride the carbon down to a metal ground source. This is exactly what you see from the third plug, where there is so much carbon build up, the spark has many carbon paths to follow.

    Here is the way mine are. My spark plug insulator tips are mostly white, while the insulator base has the ideal black ring (not to be confused with the black ring at the thread ring), while my exhaust color is a dark cream. There are two sets of plugs shown, one with 11,000 miles and one range hotter and another set with 36,000 miles. Even after that many miles, there is barely any carbon build up.

    So after nearly 50,000 miles this is how they appear. Combined with a properly tuned SuperTrapp, power and fuel economy are astounding.
    Last edited by kz550; 08-14-2011 at 04:32 PM.

  3. #3
    bschultz Guest


    Good stuff!

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