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

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

Normal:

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

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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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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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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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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.
Check the spark plug gap "L" using a gap gauge. If it is not within the standard, replace the spark plug.
CAUTION: Do not adjust the gap, because the iridium plug is used.

Standard

0.7 - 0.8 mm (0.028 - 0.031 in)

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When to See a Mechanic

Stop DIY work and contact a certified mechanic immediately if any of the following apply:

• You smell fuel, burning insulation, or see smoke.

• Brakes feel soft, pull hard to one side, or make grinding noises.

• The engine overheats, stalls repeatedly, or misfires under load.

• You are missing required tools, torque specs, or safe lifting equipment.

• You are not confident in the next step or safety outcome.

Safety Warning

Spark Plug: Inspection