Honda F401 Owner's Manual page 20

2. Visually inspect the spark plug. Discard it if the insulator is cracked or
chipped. Clean the spark plug with a wire brush if it is to be reused.
3. Measure the plug gap with a feeler gauge. The gap should be 0.7-0.8 mm
(0.028-0.031 in). Correct as necessary by bending the side electrode.
0.7-0.8 mm
(0.028-0.031 in)
4. Attach the plug washer. Thread the plug in by hand to prevent
cross-threading.
i
t
5. Tighten a new spark plug l/2 turn with the wrench to compress the washer.
If you are reusing a plug, it should only take l/8-1/4 turn after the plug
seats.
CAUTION: The spark plug must be securely tightened. An improperly
tightened plug can become very hot and possibly damage the engine. Never
use a spark plug with an improper heat range.
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