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Page 54 2007 HUV 4421 Gasoline and Diesel Vehicle Owner’s Manual
TECHNICAL & CONSUMER INFORMATION (GASOLINE ENGINES)
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 engine at altitudes above 5,000 feet (1,500 meters), have your servicing dealer perform this carburetor
modification. This engine, when operating at high altitude with the carburetor modifications for high altitude
use, will meet each emission standard throughout its useful life.
Even with carburetor notification, engine horsepower will decrease about 3.5% for each 1,000-foot (300-
meter) increase in altitude. The effect of altitude on horsepower will be greater than this if no carburetor mod-
ification is made.
NOTE: 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 (1,500 meters) 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 col-
lectively 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 infor-
mation to be posted on the pump.
The following are the EPA approved percentages of oxygenates:
ETHANOL: (ethyl or grain alcohol) 10% by volume
You may use gasoline containing up to 10% ethanol by volume. Gasoline containing etha-
nol may be marketed under the name “Gasohol”.
MTBE: (methyl tertiary butyl ether) 15% by volume
You may use gasoline containing up to 15% MTBE by volume.
METHANOL: (methyl or wood alcohol) 5% by volume
You may use gasoline containing up to 5% methanol by volume, as long as it also contains
cosolvents and corrosion inhibitors to protect the fuel system. Gasoline containing more
than 5% methanol by volume may cause starting and/or performance problems. It may also
damage metal, rubber, and plastic parts of your fuel system.
If you notice any undesirable operating symptoms, try another service station, or switch to another brand of
gasoline.
Fuel system damage or performance problems resulting from the use of an oxygenated fuel containing more
than the percentages of oxygenates mentioned above are not covered under warranty.