Honda WD20X Owner's Manual page 22

4.Check that the spark plug washer is in good condition, and thread the
spark plug in by hand to prevent cross-threading.
5.After the spark plug is seated, tighten with a spark plug wrench to
compress the washer.
- If installing a new spark plug, tighten l/2 turn after the spark plug seats
to compress the washer.
- If reinstalling a used spark plug, tighten l/8- l/4 turn after the spark plug
seats to compress the washer.
l
The spark plug must be securely tightened. An improperly tightened
spark plug can become very hot and may cause engine damage.
l
Use only the recommended spark plug or equivalent. A spark plug
which has an improper heat range may cause engine damage.
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