Honda FourTrax Rancher TRX420TM1 2020 Owner's Manual page 164

Spark Plug
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.
154 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)