Honda TRX250TE 2019 Owner's Manual page 145

7. With the plug washer attached, thread the spark plug in by hand
to prevent cross-threading.
8. 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: 1/2 turn after it seats.
b) Then loosen the plug.
c) Next, tighten the plug again:
1/8 turn after it seats.
NOTICE
An improperly tightened spark plug can damage the engine. If a
plug is too loose, the piston may be damaged. If a plug is too tight,
the threads may be damaged.
9. Connect the spark plug cap.
3/4 turn after it seats.
Spark Plug
Servicing Your Honda 135