Emission Control Systems - Honda XR125LK Owner's Manual

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GENERAL INFORMATION

EMISSION CONTROL SYSTEMS

SOURCE OF EMISSIONS
The combustion process produces carbon monoxide, oxides of nitrogen and hydrocarbons. Control of hydrocarbons and oxides
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 lean carburetor settings as well as other systems, to reduce carbon monoxide, oxides of nitrogen and
hydrocarbons.
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 and carburetor.
EXHAUST EMISSION CONTROL SYSTEM
The exhaust emission control system is composed of a pulse secondary air injection system and lean carburetor settings, no
adjustment should be made except idle speed adjustment with the throttle stop screw.
PULSE SECONDARY AIR INJECTION SYSTEM (XR125LK/LEK)
The pulse secondary air injection (PAIR) system introduces filtered air into the exhaust gases in the exhaust port. Fresh air is drawn
into the exhaust port by the function of the PAIR (Pulse Secondary Air Injection) control valve.
The reed valve prevents reverse air flow through the system. The PAIR control valve reacts to high intake manifold vacuum and will
cut off the supply of fresh air during engine deceleration, thereby preventing afterburn in the exhaust system.
No adjustments to the secondary air supply system should be made, although periodic inspection of the components is
recommended.
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