Honda EM4500CXS Manuel De L'utilisateur page 29

• High altitude operation
At high altitude, the standard carburetor air-fuel mixture will be excessively rich.
Performance will decrease, and fuel consumption will increase.
High altitude performance can be improved by specific modifications to the
carburetor. If you always operate the generator at altitudes higher than
610 meters (2,000 feet) above sea level, have your authorized Honda dealer
perform these carburetor modifications.
Even with suitable carburetor jetting, engine horsepower will decrease
approximately 3.5% for each 300 meter (1,000 foot) increase in altitude. The
affect of altitude on the horsepower will be greater than this if no carburetor
modification is made.
CAUTION:
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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