Feider Machines FMTC100, Instruction Manual, Page: 17 / 44

6.
High altitude operation
At high altitude the standard carburetor air-fuel mixture will be excessively
rich. Performance and fuel consumption will increase.
High altitude performance can be improved by installing a smaller diameter
main fuel jet in the carburetor and readjusting the pilot screw. If you always
operate the tiller at altitudes higher than 1.830m (6.000feet) above sea
level ask your authorized Motor Hoes dealer to perform these carburetor
modifications.
Even with suitable carburetor jetting, engine horsepower will decrease
approximately 3-5% for each 305m (1.000foot) increase in altitude.
The affect of altitude on the horsepower will be greater than this if no
carburetor modification is made.
CARTION: Operation of the tiller 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