Exhaust Emission Control System; Fuel Permeation Emission Control System - Honda VT750C2 Shadow Spirit Service Manual

GENERAL INFORMATION
EXHAUST EMISSION CONTROL SYSTEM
The exhaust emission control system is composed of a pulse secondary air supply system and lean carburetor settings.
No adjustment should be made except idle speed adjustment with the throttle stop screw. The exhaust emission control
system is separate from the crankcase emission control system.
SECONDARY AIR SUPPLY SYSTEM
The pulse secondary air supply 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.
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.
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
decel~ration,
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.
~
FRESHAIR
. . EXHAUST GAS
-41.'11
NEGATIVE PRESSURE
OXIDATION CATALYTIC CONVERTER (California type only)
This motorcycle is equipped with an oxidation catalytic converter.
The oxidation catalytic converter is in the exhaust system. Through chemical reactions, it converts HC and CO in the
engine's exhaust to carbon dioxide (C02) and water vapor.
FUEL PERMEATION EMISSION CONTROL SYSTEM
This motorcycle complies with the Fuel Permeation Emission regulations of the U.S. Environmental Protection Agency
(EPA), California Air Resources Board (CARB), and Environment Canada (ECl.The fuel tank, fuel hoses, and fuel vapor
charge hoses used on this motorcycle incorporate fuel permeation control technologies. Tampering with the fuel tank, fuel
hoses, or fuel vapor charge hoses to reduce or defeat the effectiveness of the fuel permeation technologies is prohibited by
federal regulations.
Revised: May 2007. 2007-2008 VT750C2
1-40