Honda GXV340 Operating And Maintenance Manual page 13

With starter motor:
Turn the engine switch to START and hold it there until the
engine starts. Do not use the electric starter for more than 5
seconds at a time. If the engine fails to start, release the switch
and wait 10 seconds before operating the starter again.
High altitude operation
At high altitude, the standard carburetor air-fuel mixture will be ex-
cessively rich. Performance will decrease, and fuel consumption
will increase.
High altitude performance can be improved by specific modifica-
tions to the carburetor. If you always operate the engine at
altitudes higher than 1,500 m (5,000 feet) above sea level, have
your authorized Honda dealer perform these carburetor modifi-
cations.
Even with suitable carburetor jetting, engine horsepower will
decrease approximately 3.5% for each 300 m (1,000 feet) increase
in altitude. The effect of altitude on the horsepower will be greater
than this if no carburetor modification is made.
Operation of the engine 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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