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, 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 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 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 are 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.
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.
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
As the power equipment engine owner, you are responsible for
completing all required maintenance listed in your owner's manual.
Honda recommends that you retain all receipts covering
maintenance on your power equipment engine, but Honda cannot
deny warranty coverage solely for the lack of receipts or for your
failure to ensure that all scheduled maintenance has been
completed.
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