Honda FourTrax Foreman TRX500FE2 2018 Owner's Manual page 178

Spark Plug
5. Inspect the electrodes and centre porcelain for deposits,
corrosion, or carbon fouling. If the corrosion or deposits are
heavy, replace the plug. Clean a carbon or wet-fouled plug with
a plug cleaner, if available, or a wire brush. Inspect the spark plug
electrodes for wear. The centre electrode (2) should have a flat tip
and sharp edges, and the side electrode (3) should not be eroded.
If the electrodes and insulator tip appear unusually fouled or
burned, we suggest that you contact your dealer.
6. Discard the spark plug if there is apparent wear or if the insulator
is cracked or chipped.
7. Using a wire-type feeler gauge, check the spark plug gap (4). If
adjustment is necessary, bend the side electrode carefully.
The gap should be:
1.00 – 1.10 mm (0.039 – 0.043 in)
1.00 – 1.10 mm
(0.039 – 0.043 in)
(2) centre electrode
(3) side electrode
168
Servicing Your Honda
(4)
(4) spark plug gap
(3)
(2)