Honda EU20i Owner's Manual page 45

Visually inspect the spark plug. Discard it if the insulator is cracked,
5.
chipped, or fouled. Clean the spark plug with a wire brush if it is to
be reused.
6. Measure the plug gap with a feeler gauge.
Correct as necessary by carefully bending the side electrode.
The gap should be:
0.6 0.7 mm (0.024 0.028 in)
0.6 0.7 mm
(0.024 0.028 in)
7. Install the spark plug carefully, by hand, to avoid cross-threading.
8. After a new spark plug has been seated by hand, it should be
tightened 1/2 turn with a wrench to compress its washer.
If a used plug is being reinstalled, it should only require 1/8 to 1/4
turn after being seated.
9. Reinstall the spark plug cap on the spark plug securely.
10. Reinstall the spark plug maintenance cover.
The spark plug must be securely tightened. An improperly
tightened plug can become very hot and possibly damage the
generator.
Never use a spark plug with an improper heat range.
SIDE ELECTRODE
43