Exhaust Emission Control System - Honda Nighthawk CB 750 1991 Service Manual

General Information
Exhaust Emission Control System
(Except California model)
The exhaust emission control system is composed of lean carburetor settings and no adjustment should be made except
idle speed adjustment with the throttle stop screw.
(California moddl
The exhaust emission control system consists of a pulse secondary air supply system which introduces filtered air into the exhaust
gases in the exhaust port. Fresh air is drawn into the exhaust port whenever there is a negative pressure pulse in the
exhaust system. This charge of fresh air promotes burning of the unburned exhaust gases and changes a considerable
amount of hydrocarbons and carbon monoxide into relatively harmless carbon dioxide and water vapor.
A pulse secondary air injection check valve (PAIR check valve) prevents reverse air flow through the system. The pulse
secondary air injection control valve (PAIR control valve) reacts to high intake manifold vacuum and will cut off the supply
of fresh air during engine deceleration, thereby preventing afterburn i n the exhaust system.
No adjustments t o the pulse secondary air supply system should be made, although periodic inspection of the
components is recommended.
(California Model Only)
(2) CARBURETOR
(1)INTAKE PORT
I
/
CONTROL VALVE
(4) PAIR CHECK VALVE
: (6):FRESH AIR