Carburetor Modifications For High Altitude Operation; Emission Control System Information - Honda GCV520 Manuel De L'utilisateur

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 Act, 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.
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