Honda GXH50 Owner's Manual page 36

SERVICING YOUR HONDA ENGINE
6. After the spark plug seats, tighten with a 5/8-inch spark plug wrench to
compress the washer.
If reinstalling the used spark plug, tighten 1/8-1/4 turn after the spark plug
seats.
If installing a new spark plug, tighten 1/2 turn after the spark plug seats.
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A loose spark plug can overheat and damage the engine.
Overtightening the sparkplug can damage the threads in the cylinder head.
7. Attach the spark plug cap.
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