Technical Information; Serial Number Locations; Carburetor Modification For High Altitude Operation; Emission Control System - Honda HS520A Owner's Manual

TECHNICAL INFORMATION

SERIAL NUMBER LOCATIONS

ENGINE SERIAL NUMBER
Use a flashlight to view through the
hole for the exhaust pipe. The
number starts with "GC..."
FRAME SERIAL
NUMBER
There are two serial numbers, one for the engine and one for the
frame. Record the engine and frame serial numbers and date of
purchase in the spaces below. You will need these serial numbers
when ordering parts and when making technical or warranty inquiries.
Engine serial number:_____________________________________
Frame serial number: _____________________________________
Date of purchase: ________________________________________
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 snowthrower 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-foot (300-meter) increase in altitude. The
effect of altitude on horsepower will be greater than this if no
carburetor modification is made.
ENGINE NOTICE
SERIAL
When the carburetor has been modified for high altitude operation,
NUMBER
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.

EMISSION CONTROL SYSTEM

Source of Emissions
The combustion process produces carbon monoxide, oxides of
nitrogen, and hydrocarbons. Control of hydrocarbons and oxides of
nitrogen is very important because, under certain conditions, they
react to form photochemical smog when subjected to sunlight. Carbon
monoxide does not react in the same way, but it is toxic.
Honda utilizes appropriate air/fuel ratios and other emissions control
systems to reduce the emissions of carbon monoxide, oxides of
nitrogen, and hydrocarbons.
The U.S., California Clean Air Act, and Environment
Canada
EPA, California, and Canadian regulations require all manufacturers
to furnish written instructions describing the operation and
maintenance of emissions control systems.
The following instructions and procedures must be followed in order to
keep the emissions from your Honda engine within the emissions
standards.
Tampering and Altering
NOTICE
Tampering is a violation of Federal and California law.
Tampering with or altering the emissions control system may increase
emissions beyond the legal limit. Among those acts that constitute
tampering are:
• Removal or alteration of any part of the intake, fuel, or exhaust
systems.
• Altering or defeating the speed-adjusting mechanism to cause the
engine to operate outside its design parameters.
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