Honda EM4000SX Owner's Manual page 52

SERVICING YOUR GENERATOR
3. Visually inspect the spark plug. Replace it if the electrodes are worn
or if the insulator is cracked, chipped, or fouled.
4. Measure the spark plug electrode gap with a wire-type feeler gauge.
Correct the gap, if necessary, by carefully bending the side electrode.
The gap should be:
0.028 0.031 in (0.7 0.8 mm)
5. Check that the spark plug sealing washer is in good condition, and
thread the spark plug in by hand to prevent cross-threading.
6. After the spark plug is seated, tighten with a spark plug wrench to
compress the washer.
If installing a new spark plug, tighten 1/2 turn after the spark plug
seats to compress the washer. If reinstalling a used spark plug,
tighten 1/8 1/4 turn after the spark plug seats to compress the
washer.
A loose spark plug can overheat and damage the engine.
Overtightening the spark plug can damage the threads in the cylinder
head.
7. Attach the spark plug cap.
50
SIDE ELECTRODE
0.028 0.031 in (0.7 0.8 mm)
SEALING WASHER