Carburetor Modification For High Altitude Operation - Honda HHH25D Manuel De L'utilisateur

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 hedge trimmer at altitudes above 610 m
(2,000 ft.), 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 m (1,000 ft.) increase in altitude. The effect of altitude on horsepower
will be greater than this if no carburetor modification is made.
CAUTION:
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 m (2,000 ft.) 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.
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