Spark Plug: Inspection

1. Check the spark plug for damage. If defective, replace the spark plug.

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2. Check the spark plug electrode and condition of the insulator. If abnormal, check and repair the cause and replace the spark plug.
   1. Normal:

      Brown to grayish-tan deposits and slight electrode wear indicate correct spark plug heat range.

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   2. Carbon fouled:

      Dry fluffy carbon deposits on the insulator and electrode are mostly caused by slow-speed driving in town, weak ignition, too rich fuel mixture, etc.

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   3. Oil fouled:

      Wet black deposits show oil entrance into combustion chamber through worn piston rings or increased clearance between valve guides and valve stems.

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   4. Overheating:

   A white or light gray insulator with black or brown spots and bluish burnt electrodes indicate engine overheating, wrong selection of fuel, or loose spark plugs.

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3. Using a nylon brush, etc., clean and remove the carbon or oxide deposits from the spark plug. If deposits are too stubborn, replace the spark plugs.
   NOTE:

   • Never use a plug cleaner.
   • Do not use a metal brush as it may damage the electrode area.
4. Check the spark plug gap "L" using a gap gauge. If it is not within the standard, replace the spark plug.

Standard 

0.5 - 0.6 mm (0.020 - 0.024 in)

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