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. High altitude performance can be improved by
specific modifications to the carburetor. If you always operate your
mower at altitudes above 5,000 feet (1,524 meters) have an
authorized Honda servicing dealer perform this carburetor
modification. Even with modification, horsepower will decrease
about 3.5% for each 1,000 ft (300 m) increase in altitude. The
effect of altitude on horsepower will be greater than this if no
carburetor modification is made.
NOTICE
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 an
authorized Honda servicing dealer return the carburetor to original
factory specifications.
Fuel Recommendations
Use unleaded gasoline with a pump octane rating of 86 or higher.
This engine is certified to operate on unleaded gasoline. Unleaded
gasoline produces fewer engine and spark plug deposits and
extends exhaust system life. Never use stale or contaminated
gasoline or an oil/gasoline mixture. Avoid getting dirt or water in
the fuel tank. Occasionally you may hear light “spark knock” or
“pinging” (metallic rapping noise) while operating under heavy
loads. This is no cause for concern. If spark knock or pinging
occurs at a steady engine speed, under normal load, change
brands of gasoline. If spark knock or pinging persists, see an
authorized Honda servicing dealer.
NOTICE
Running the engine with persistent spark knock or pinging can
cause engine damage. Running the engine with persistent spark
knock or pinging is misuse, and the Distributor’s Limited Warranty
(page 51) does not cover parts damaged by misuse. For
oxygenated fuel information refer to page 58.
MAINTENANCE
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