Carburetor Modifications For High Altitude Operation; Emission Control System Information - Honda Car Engine GX340 Owner's Manual

Carburetor Modifications for High Altitude Operation

At high altitude, the standard carburetor air-fuel mixture will be
too rich. Performance will decrease, and fuel consumption will
increase. A very rich mixture will also foul the spark plug and
cause hard starting. Operation at an altitude that differs from that
at which this engine was certified, for extended periods of time,
may increase emissions.
High altitude performance can be improved by specific
modifications to the carburetor. If you always operate your engine
at altitudes above 1,500 meters (5,000 feet), have your servicing
dealer perform this carburetor modification. This engine, when
operated at high altitude with the carburetor modifications for
high altitude use, will meet each emission standard throughout its
useful life.
Even with carburetor modification, engine horsepower will
decrease about 3.5% for each 300-meter (1,000-foot) increase in
altitude. The effect of altitude on horsepower will be greater than
this if no carburetor modification is made.
When the carburetor has been modified for high altitude operation,
the air-fuel mixture will be too lean for low altitude use. Operation
at altitudes below 1,500 meters (5,000 feet) with a modified
carburetor may cause the engine to overheat and result in serious
engine damage. For use at low altitudes, have your servicing
dealer return the carburetor to original factory specifications.

Emission Control System Information

Source of Emissions
The combustion process produces carbon monoxide, oxides of
nitrogen, and hydrocarbons. Control of hydrocarbons and oxides
of 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 utilizes appropriate air/fuel ratios and other emissions
control systems to reduce the emissions of carbon monoxide,
oxides of nitrogen, and hydrocarbons.
Additionally, Honda fuel systems utilize components and control
technologies to reduce evaporative emissions.
The U.S., California Clean Air Acts and Environment Canada
EPA, California and Canadian regulations require all
manufacturers to furnish written instructions describing the
operation and maintenance of emission control systems.
The following instructions and procedures must be followed in
order to keep the emissions from your Honda engine within the
emission standards.
Tampering and Altering
Tampering with or altering the emission control system may
increase emissions beyond the legal limit. Among those acts that
constitute tampering are:
Removal or alteration of any part of the intake, fuel, or exhaust
systems.
Altering or defeating the governor linkage or speed-adjusting
mechanism to cause the engine to operate outside its design
parameters.
Problems That May Affect Emissions
If you are aware of any of the following symptoms, have your
engine inspected and repaired by your servicing dealer.
Hard starting or stalling after starting.
Rough idle.
Misfiring or backfiring under load.
Afterburning (backfiring).
Black exhaust smoke or high fuel consumption.
Replacement Parts
The emission control systems on your Honda engine were
designed, built, and certified to conform with EPA, California
(models certified for sale in California), and Canadian emission
regulations. We recommend the use of Honda Genuine parts
whenever you have maintenance done. These original-design
replacement parts are manufactured to the same standards as the
original parts, so you can be confident of their performance. The
use of replacement parts that are not of the original design and
quality may impair the effectiveness of your emission control
system.
A manufacturer of an aftermarket part assumes the responsibility
that the part will not adversely affect emission performance. The
manufacturer or rebuilder of the part must certify that use of the
part will not result in a failure of the engine to comply with
emission regulations.
Maintenance
Follow the maintenance schedule on page . Remember that this
schedule is based on the assumption that your machine will be
used for its designed purpose. Sustained high-load or high-
temperature operation, or use in unusually wet or dusty conditions,
will require more frequent service.
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