Honda CRF250F 2020 Owner's Manual page 158

Source of Emissions
The combustion process produces carbon
monoxide (CO), oxides of nitrogen (NOx), and
hydrocarbons (HC). Control of hydrocarbons
and oxides of nitrogen is very important
because, under certain conditions, they react to
form photochemical smog when subjected to
sunlight. Carbon monoxide does not react in
the same way, but it is toxic.
Honda Motor Co., Ltd. utilizes various systems
to reduce carbon monoxide, oxides of nitrogen
and hydrocarbons.
Emission Control Systems
Exhaust Emission Control System
The exhaust emission control system includes a
PGM-FI system.
No adjustment to this system should be made
although periodic inspection of the components
is recommended.
The exhaust emission control system is
separate from the crankcase emission control
system.
Technical Information
151