Carburetor Modification For High Altitude Operation - Honda Power Products 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 1,500 m (5,000 ft.), have your authorized Honda 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 1,500 m (5,000 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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