Carburetor Modification For High Altitude Operation - Honda FQ650 Owner's Manual

TECHNICAL & CONSUMER INFORMATION

Carburetor Modification 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 tiller at altitudes above 610 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 610
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 specification.
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