Honda FourTrax Rancher TRX420FA5 2019 Owner's Manual page 134

Fuel
Fuel Capacity
Fuel tank capacity, including reserve:
3.88 US gal (14.7 ℓ)
Reserve capacity:
1.29 US gal (4.9 ℓ)
When there is only one segment left in the fuel gauge (page 25), fuel
will be low and you should refuel as soon as possible.
Refueling Procedure
Refer to Safety Precautions on page 107.
(1) fuel fill cap
(2) bottom of filler neck
124 Servicing Your Honda
(1)
(2)