Honda FourTrax Rancher TRX420TM1 2020 Owner's Manual page 247

Crankcase Emission Control System
The engine is equipped with a Closed Crankcase System to prevent
discharging crankcase vapors into the atmosphere. Blow-by gas is
returned to the combustion chamber through the air cleaner,
throttle body and intake-manifold.
Problems That May Affect ATV Exhaust Emissions
If you are aware of any of the following symptoms, have the vehicle
inspected and repaired by your ATV dealer.
Symptoms:
1. Hard starting or stalling after starting
2. Rough idle
3. Misfiring or backfiring during acceleration
4. After-burning (backfiring)
5. Poor performance (driveability) and poor fuel economy
Federal regulations prohibit removing or disabling a device or
element of design that may affect your engine's emission
performance unless your ATV will be used exclusively in competition.
If you modify your engine for use in sanctioned competition events,
you must deface or destroy the emission control information label.
If you loan, sell, or give your competition modified Honda ATV to
someone else, under applicable law, you must inform the new
owner/operator in writing that the vehicle is to be used for
competition only.
Emission Control Systems
Technical Information 237