Carburetor Modification For High Altitude Operation - Honda EU20i Owner's Manual

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 generator at altitudes
above 1,500 meters (5,000 feet), 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-meter (1,000-foot) increase in altitude. The ef-
fect of altitude on horsepower will be greater than this if no carburetor
modification is made.
Operation of the generator at an altitude lower than the carburetor is
jetted for may result in reduced performance, overheating, and
serious engine damage caused by an excessively lean air/fuel mixture.
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