Honda TRX500FA 2006 Owner's Manual page 184

10. With the plug washer attached, thread the spark plug in by hand to
prevent cross-threading.
11. Tighten the spark plug:
If the old plug is good:
1/8 turn after it seats.
If installing a new plug, tighten it twice to prevent loosening:
a) First, tighten the plug:
NGK:
DENSO:
b) Then loosen the plug.
c) Next, tighten the plug again:
1/8 turn after it seats.
Improperly tightened spark plug can damage the engine. If a plug is too
loose, a piston may be damaged. If a plug is too tight, the threads may
be damaged.
12. Reinstall the spark plug cap. Take care to avoid pinching any cables
or wires.
13. Install the remaining parts in the reverse order of removal.
3/4 turn after it seats.
1/2 turn after it seats.
Spark Plug
Servicing Your Honda
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