High Altitude Operation - Honda F660 Manuel De L'utilisateur

6. Let the engine warm up for several minutes. If the choke has been
pulled out to the CLOSE position, return it gradually to the OPEN
position as the engine warms up.

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 tiller at altitude higher than
1,500 m (5,000 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 m (1,000 foot) increase in altitude.
The effect of altitude on horsepower will be greater than this if no
carburetor modification is made.
Operation of the tiller at an altitude lower than the carburetor is jetted
for may result in reduced performance, overheating, and serious en-
gine damage caused by an excessively lean air-fuel mixture.
22
CHOKE KNOB
OPEN