Honda BIG RED 2009 Owner's Manual page 203

Emission Control Systems
Source of Exhaust 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.
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.
Crankcase Emission Control System
The engine is equipped with a closed crankcase system to prevent
discharging crankcase emissions into the atmosphere. Blow-by gas is
returned to the combustion chamber through the air cleaner.
194 Technical Information