Honda Harmony HS520A Owner's Manual page 28

SERVICING YOUR HONDA SNOWTHROWER
A replacement spark plug may be purchased from a servicing
Honda snowthrower dealer. See page 49 for a part number list.
SPARK PLUG: BPR5ES (NGK) or W16EPR-U (DENSO)
3. Measure the plug gap with a feeler
gauge. Correct as necessary by
bending the side electrode.
PLUG GAP: 0.028 - 0.031 inch
(0.70 - 0.80 mm)
4. Make sure that the spark plug washer
is in good condition, and thread the
spark plug in by hand to prevent cross-
threading.
5. 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 to 1/4 turn after the spark plug seats.
NOTICE
The spark plug must be securely tightened. An improperly
tightened spark plug can become hot and may damage the engine.
6. Connect the spark plug cap and close the spark plug access panel.
26
0.028 ~ 0.031 inch
(0.70 ~ 0.80 mm)