Honda FG400 Owner's Manual page 38

SERVICING YOUR HONDA TILLER
If reinstalling a 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.
A loose spark plug can overheat and damage the engine.
Overtightening the sparkplug can damage the threads in the cylinder he
7 Attach the spark plug cap.
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