PERIODIC MAINTENANCE 2-15
HEAT RANGE
• Check spark plug heat range by observing electrode color. If
the electrode of the spark plug is wet appearing or dark color,
replace the spark plug with hotter type one. If it is white or
glazed appearing, replace the spark plug with colder type
one.
NOTE:
“R” type spark plug has a resistor built into at the center elec-
trode to prevent radio noise.
CARBON DEPOSITS
• Check carbon deposits on the spark plug.
• If carbon is deposited, remove it using a spark plug cleaner
machine or carefully use a tool with a pointed end.
SPARK PLUG GAP
• Measure the spark plug gap with a thickness gauge.
• Adjust the spark plug gap if necessary.
% Spark plug gap
A
Standard: 0.6 – 0.7 mm (0.024 – 0.028 in)
& 09900-20803: Thickness gauge
ELECTRODE’S CONDITION
• Check the condition of the electrode.
• If it is extremely worn or burnt, replace the spark plug.
Replace the spark plug if it has a broken insulator, damaged
thread, etc.
"
Hot type Standard Cold type
NGK CR7EK CR8EK CR9EK
ND U22ETR U24ETR U27ETR
Confirm the thread size and reach when replacing the
plug. If the reach is too short, carbon will be deposited
on the screw portion of the plug hole and engine dam-
age may result.
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