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After studying this chapter, you will be able to:
• Perform preventive maintenance on various
engine systems, including the crankcase
breather, air cleaner, and muffl er.
• Keep engines clean.
• Change the oil in a four-cycle engine.
• Prepare an engine for storage.
• Describe systematic troubleshooting.
• Use manufacturer’s service manuals to
determine engine specifi cations and explain
why this information is necessary when
servicing a small engine.
C H A P T E R 1 3
Preventive Maintenance
and Troubleshooting
Learning Objectives Key Terms
compression gauge
compression test
coolant hydrometer
differential pressure test
digital tachometer
fi ller plug
hot spots
loaded oil
optical tachometer
owner’s manual
preventive maintenance
reverse fl ushing
service manual
systematic
troubleshooting
thread chaser
Preventive Maintenance
Certain maintenance tasks must be performed
regularly to keep an engine working properly.
These tasks come under the heading of preventive
maintenance, because they help prevent prema-
ture engine wear and other engine problems.
Engine Cleaning
Cleaning a small air-cooled engine periodically
can help prevent overheating. For proper cooling
action, air must pass across the extended metal
surfaces (cooling fi ns) of the cylinder block and
cylinder head. If the cooling fi ns are insulated by
dirt, leaves, and/or grass clippings, engine parts
will retain most of the combustion heat. Parts will
expand, probably distort, and possibly seize. There-
fore, all fi nned surfaces should be cleaned regularly.
Methods for cleaning small air-cooled engines
vary. Begin by removing any shrouds or engine
covers obstructing the cooling fi ns. You can then
blow debris from the fi ns with compressed air and
use a cleaning solvent to remove any remaining dirt
and oil. See Figure 13-1. Alternately, you can scrape
the dirty areas with a piece of wood and wipe them
with a clean cloth. Various multipurpose spray
cleaners are suitable for use on small engines.
When using compressed air, be extremely careful
where you direct the blast of air. Wear safety goggles.
Never direct the air blast toward skin or clothing.
In addition to cleaning cooling fi ns, be sure to
clean the engine crankcase area. This area also trans-
fers a great deal of engine heat to the surrounding
air. A coating of dirt or oil will insulate the crankcase
and may contribute to engine overheating.
Warning