Honda Power Products WB20XT Guide De L'utilisateur page 28

4. Check that the spark plug washer is in good condition, and thread
the spark plug in by hand to prevent cross-threading.
NOTE:
If installing a new spark plug, tighten 1/2 turn after the spark plug
seats to compress the washer. If reinstalling a used spark plug, tighten
1/8—1/4 turn after the spark plug seats to compress the washer.
CAUTION:
The spark plug must be securely tightened. An improperly tightened
spark plug can become very hot and may cause engine damage.
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