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Section 4 Engine Service
If necessary, fi ll the fuel tank. If you are servic-
ing a two-stroke engine, make sure the proper fuel-
oil mixture is added to the tank. See Chapter 11 for
additional information on mixing oil and fuel.
Start the engine and let it idle until warm.
Adjust the idle speed if necessary. Increase the
engine speed in the normal manner. Make a brief
test run while listening to the engine and watch-
ing the condition of all parts.
Storing Liquid-Cooled Engines
In addition to the storage precautions cov-
ered previously, storing liquid-cooled engines for
lengthy periods, particularly during winter, calls
for special maintenance procedures. If the engine
has a pressurized system, the coolant must be
strong enough to protect against freezing at the
lowest possible temperatures.
If the engine will not be started at any time dur-
ing storage, drain the cooling system completely.
Then, tag the engine to indicate its drained condition.
When storing outboard engines, remove all
plugs from the gearcase and drive shaft housing.
This allows accumulated water in the gearcase
and cooling system to drain off.
Failure to take this precaution when winteriz-
ing may result in a cracked cylinder block and/or
gearcase, plus possible damage to water channels
and tubes.
Rock the engine from side to side to make
certain all water has drained. Refi ll the gearcase
with the type of lubricant specifi ed by the engine
manufacturer. Attend to all other lubrication rec-
ommendations made by the manufacturer for care
of the engine being stored.
Systematic Troubleshooting
Most small engine service and repair jobs can
be done without taking the entire engine apart.
If the engine will not start, is hard to start, runs
rough, or lacks power, troubleshooting may be
necessary. Troubleshooting is simply a number of
tests and steps you go through to fi nd a problem.
Sometimes the cause of an engine problem is
easy to fi nd. At other times, checking probable
causes requires a certain amount of reasoning and
the use of the process of elimination. Also, more
than one fault can exist at the same time, making it
harder to locate the trouble.
Always take a systematic approach when trouble-
shooting small engines. Systematic troubleshooting
involves checking and/or testing one component after
another component until the problem is located and
corrected. There are two basic principles to keep in
mind when trying to pinpoint small engine problems:
• Check the easiest things fi rst.
• Verify the fundamental operating requirements.
Check the Easiest Things First
Always start troubleshooting by checking for
the simplest, most probable problems fi rst. If an
engine will not start, the problem could be some-
thing as simple as an empty fuel tank or a discon-
nected spark plug wire. Do not start working on
the carburetor or ignition system until you have
made a few basic checks to determine that a simple
remedy will not cure the problem.
Verify the Fundamental
Operating Requirements
In order to start and run properly, an engine
must meet fi ve fundamental operating require-
ments. These requirements include:
• Proper carburetion—Clean, fresh fuel must
be delivered in the correct proportion with
combustion air.
• Correct ignition system operation—A strong
ignition spark must be precisely timed for
best performance and effi ciency.
• Adequate lubrication—The proper amount of
high-quality lubricating oil must reach critical
engine components.
• Suffi cient cooling—An ample supply of
cooling air must reach engine.
• Proper compression—Compression should
have 30–45 psi minimum for starting and
90 psi minimum for effi cient operation and
suffi cient power.
Keep these operating requirements in mind when
troubleshooting small gas engines. Through the pro-
cess of elimination, you can easily isolate problems.
For example, if an engine will not start but will spin
normally, you can eliminate lubrication system prob-
lems because the engine is not locked-up. By spin-
ning the engine, you can also determine whether or
not it has suffi cient compression. If the engine will
not start after it has cooled down, the cooling system