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12. TECHNICAL & CONSUMER INFORMATION
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 pump at altitudes above 5,000 feet (1,500
meters), have your 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 1,000 feet (300 meters) increase in altitude. The effect of altitude on
horsepower will be greater than this if no carburetor modification is made.
When the carburetor has been modified for high altitude operation, the
air-fuel mixture will be too lean for low altitude use. Operation at altitudes
below 5,000 feet (1,500meters) with a modified carburetor may cause the
engine to overheat and result in serious engine damage. For use at low
altitudes, have your servicing dealer return the carburetor to original
factory specifications.
Oxygenated Fuels
Some conventional gasolines are being blended with alcohol or an ether
compound. These gasolines are collectively referred to as oxygenated fuels. To
meet clean air standards, some areas of the United States and Canada use
oxygenated fuels to help reduce emissions.
If you use an oxygenated fuel, be sure it is unleaded and meets the minimum
octane rating requirement.
Before using an oxygenated fuel, try to confirm the fuel’s contents. Some
states/provinces require this information to be posted on the pump.
The following are the EPA-approved percentages of oxygenates:
ETHANOL
——
(ethyl or grain alcohol) 10% by volume.
