Honda BF40D Owner's Manual page 81

New plug Plug needing
replacement
4. Inspect the spark plugs. Replace
them if the electrodes are worn, or
if the insulators are cracked or
chipped.
SERVICING YOUR OUTBOARD MOTOR
SIDE ELECTRODE
0.024 – 0.028 in
(0.6 – 0.7 mm)
SEALING WASHER
INSULATOR
5. 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:
0.024 – 0.028 in (0.6 – 0.7 mm)
SPARK PLUG
6. Install the spark plugs carefully, by
hand, to avoid cross-threading.
7. After each spark plug seats, tighten
with a spark plug wrench to
compress the sealing washer.
If reinstalling used spark plugs,
tighten 1/8 – 1/4 turn after the
spark plugs seat.
If installing new spark plugs,
tighten 1/2 turn after the spark
plugs seat.
Loose spark plugs can overheat
and damage the engine.
Overtightening the spark plugs can
damage the threads in the cylinder
head.
8. Attach the spark plug caps.
9. Install and lock the engine cover.
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