2005-2009 Honda TRX400EX/TRX400X Service Manual, Page 32Get this manual
GENERAL INFORMATION
EMISSION CONTROL SYSTEMS
The .SEnvironmental Protection Agency (EPA) and the California Air Resources Board (CARB) requi re that ATV comp ly ith applicable exhaust emissions st andards during its useful life, when operated and maintained according to the instruction provided
SOURCE OF EMISSIONS
The combustion process produces carbon monoxide, oxides of nitrogen and hydrocar bonsControl of hydrocarbons and oxides of nitrogen is very important becauseunder certa in conditions, they react to form photochemical smog when subjected to sunl ightCarbon monoxide does not react in the same way, but it is toxicHonda Motor Co Ltd utilizes appropriate carburetor settings as well as other systems, to reduce oxides of nitrogencarbon monox ide and hydrocarbons
EXHAUST EMISSION CONTROL SYSTEM
The exhaust em ission control system is composed of appropriate carburetor setting, and no adjustments should be made except idle speed adj ustment with the thro ttl stop screw The exhaust em ission control system is separate from the crankcase emission control systems