Honda TRX450ER Owner's Manual page 133

Spark Plug
6. With the plug washer attached, thread the spark plug in by hand to
prevent cross-threading.
7. 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: 3/4 turn after it seats.
DENSO: 1/2 turn after it seats.
b) Then loosen the plug.
c) Next, tighten the plug again:
1/8 turn after it seats.
An 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.
8. Connect the spark plug cap. Take care to avoid pinching any cables or
wires.
124 Servicing Your Honda