Honda FourTrax Rancher TRX420FE1 2019 Owner's Manual page 162

Spark Plug
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:
0.039 – 0.043 in (1.00 – 1.10 mm)
LEFT SIDE
(1)
(1) spark plug cap
(2) center electrode
8. With the plug washer attached, thread the spark plug in by hand
to prevent cross-threading.
9. Tighten the spark plug:
• If the old plug is good:
1/8 turn after it seats.
• If installing a new plug, tighten it twice to prevent loosening:
a) First, tighten the plug:
NGK:
DENSO: 1/2 turn after it seats.
b) Then loosen the plug.
c) Next, tighten the plug again:
1/8 turn after it seats.
152 Servicing Your Honda
3/4 turn after it seats.
0.039 – 0.043 in
(1.00 – 1.10 mm)
(4)
(3) side electrode
(4) spark plug gap
(3)
(2)