Honda GXV390, Owner'S Manual

ENGLISH

15

Carburetor Modifications 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 
610 meters (2,000 feet), 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 300 meter (1,000 foot) 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 
610 meters (2,000 feet) 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 INFORMATION

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.
Additionally, Honda fuel systems utilize components and control 
technologies to reduce evaporative emissions.

The U.S. and California Clean Air Acts, and Environment and Climate 
Change Canada (ECCC)

U.S. EPA, California and Canadian regulations require all manufacturers to 
furnish written instructions describing the operation and maintenance of 
emission control systems.
The following instructions and procedures must be followed in order to 
keep the emissions from your Honda engine within the emission 
standards.

Tampering and Altering

Tampering is a violation of federal and California law.

Tampering with or altering the emission control system may increase 
emissions beyond the legal limit. Among those acts that constitute 
tampering are:

• Removal or alteration of any part of intake, fuel, or exhaust systems.
• Alterations that would cause the engine to operate outside its design 

parameters.

Problems That May Affect Emissions

If you are aware of any of the following symptoms, have your engine 
inspected and repaired by your authorized Honda Power Equipment 
dealer.

• Hard starting or stalling after starting.
• Rough  idle.
• Misfiring or backfiring under load.
• Afterburning (backfiring).
• Black exhaust smoke or high fuel consumption.

Replacement Parts

The emissions control systems on your new Honda engine were 
designed, built, and certified to conform with EPA, California (models 
certified for sale in California only), and Canadian emissions regulations.   
We recommend the use of Honda Genuine parts whenever you have 
maintenance done. These original design replacement parts are 
manufactured to the same standards as the original parts, so you can be 
confident of their performance. Honda cannot deny coverage under the 
emission warranty solely for the use of non-Honda replacement parts or 
service performed at a location other than an authorized Honda 
dealership; you may use comparable EPA certified parts, and have service 
performed at non-Honda locations. However, the use of replacement 
parts that are not of the original design and quality may impair the 
effectiveness of your emissions control system.
A manufacturer of an aftermarket part assumes the responsibility that 
the part will not adversely affect emissions performance. The 
manufacturer or rebuilder of the part must certify that use of the part will 
not result in a failure of the engine to comply with emissions regulations.

Maintenance

As the power equipment engine owner, you are responsible for 
completing all required maintenance listed in your owner's manual. 
Honda recommends that you retain all receipts covering maintenance on 
your power equipment engine, but Honda cannot deny warranty 
coverage solely for the lack of receipts or for your failure to ensure that all 
scheduled maintenance has been completed.
Follow the "MAINTENANCE SCHEDULE" on page 7.
Remember that this schedule is based on the assumption that your 
Honda engine product will be used for its designed purpose. Sustained 
high-load or high-temperature operation, or use in dusty conditions, will 
require more frequent service.

Air Index
(Models certified for sale in California)

An Air Index Information label is applied to engines certified to an 
emission durability time period in accordance with the requirements of 
the California Air Resources Board.
The bar graph is intended to provide you, our customer, the ability to 
compare the emissions performance of available engines. The lower the 
Air Index, the less pollution.
The durability description is intended to provide you with information 
relating to the engine’s emission durability period. The descriptive term 
indicates the useful life period for the engine’s emission control system. 
See your "EMISSION CONTROL SYSTEM WARRANTY" (see page 16) for 
additional information.

Descriptive Term

Applicable to Emissions Durability Period

Moderate

      50 hours (0–80 cc, inclusive)
    125 hours (greater than 80 cc)

Intermediate

    125 hours (0–80 cc, inclusive)
    250 hours (greater than 80 cc)

Extended

    300 hours (0–80 cc, inclusive)
    500 hours (greater than 80 cc)
 1,000 hours (225 cc and greater)

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