Honda Metropolitan CHF50, Service Manual, Page: 42 / 319

GENERAL INFORMATION
1-38
EXHAUST EMISSION CONTROL SYSTEM (After ’05 model)
SECONDARY AIR SUPPLY SYSTEM
The secondary air supply system 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.
No adjustment to the PAIR system should be made, although periodic inspection of the components is recommended.
OXIDATION CATALYTIC CONVERTER
This scooter is equipped with an oxidation catalytic converter.
This oxidation catalytic converter is in the exhaust system. Through chemical reactions, it converts HC and CO in the
engine’s exhaust to carbon dioxide (CO
2
) and water vapor.
NOISE EMISSION CONTROL SYSTEM
TAMPERING WITH THE NOISE CONTROL SYSTEM IS PROHIBITED: U.S. Federal law prohibits, or Canadian provincial law
may prohibit the following acts or the causing thereof: (1) The removal or rendering inoperative by any person, other tan
for purposes of maintenance, repair or replacement, of any device or element of design incorporated into any vehicle for
the purpose of noise control prior to its sale or delivery to the ultimate customer or while it is in use; (2) the use of the
vehicle after such device or element of design has been removed or rendered inoperative by any person.
AMONG THOSE ACTS PRESUMED TO CONSTITUTE TAMPERING ARE THE ACTS LISTED BELOW:
1. Removal of, or puncturing of the muffler, baffles, header pipes or any other component which conducts exhaust gases.
2. Removal of, or puncturing of any part of the intake system.
3. Lack of proper maintenance.
4. Replacing any moving parts of the vehicle, or parts of the exhaust or intake system, which parts other then those
specified by the manufacturer
FUEL PERMEATION EMISSION CONTROL SYSTEM (After ’07)
This scooter complies with the Fuel Permeation Emission Control regulations of the U.S. Environmental Protection Agency
(EPA), California Air Resources Board (CARB), and Environment Canada (EC). The fuel tank and fuel hoses used on the
scooter incorporate fuel permeation control technologies. Tampering with the fuel tank or fuel hoses to reduce or defeat
the effectiveness of the fuel permeation technologies is prohibited by federal regulations.
EXHAUST PORT
PAIR CHECK VALVE
AIR CLEANER
FRESH AIR
EXHAUST GAS