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This section contains important information about serial number
locations, high altitude operation, and emission control systems.
Serial Number Locations
There are two serial numbers, one for the trimmer and one for the
engine. Record these numbers in the space provided. You will need to
have these numbers available when ordering parts or making
technical or warranty inquiries
Engine serial number: _____________________________
Frame serial number: ______________________________
Date of purchase: _________________________________
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 trimmer 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.
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.
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.
Esco utilizes appropriate air/fuel ratios and other emission control
systems to reduce the emissions of carbon monoxide, oxides of
nitrogen, and hydrocarbons. Additionally, Esco fuel systems utilize
components and control technologies to reduce evaporative

The U.S., California Clean Air Act, and Environment
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 Esco engine within the emission

Tampering and Altering
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 the intake, fuel, or exhaust
• Altering or defeating the speed-adjusting mechanism to 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 servicing 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 emission control systems on your new Esco engine were
designed, built, and certified to conform with EPA, California and
Canadian emission regulations. We recommend the use of Esco
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. The use of replacement parts that are not of the original
design and quality may impair the effectiveness of your emission
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 emission

Follow the MAINTENANCE SCHEDULE. Remember this
schedule is based on the assumption that your machine will be used
for its designed purpose. Sustained high-load or high-temperature
operation, or use in unusually wet or dusty conditions, will require
more frequent service
Air Index
An Air Index Information hang tag/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 the engine’s emission durability period. The descriptive term
indicates the useful life period for the engine’s emission control
for additional information.

 Term Applicable to Emission
 Durability Period
 Moderate  50 hours (0 ~ 80 cc)
125 hours (greater than 80 cc)
 Intermediate  125 hours (0 ~ 80 cc)
250 hours (greater than 80 cc)
 300 hours (0 ~ 80 cc)
500 hours (greater than 80 cc)
1000 hours (225 cc and greater)