9-1
CHAPTER 9. TROUBLESHOOTING & TESTING
ENGINE KNOCKS
1. Check the crankshaft coupler or pulley for loose fit,
loose bolts or crankshaft key damage. Remove,
inspect, and replace as necessary. Re-install and
re-torque the bolts to the proper specifications of
the OEM.
2. Check the flywheel key and keyways for wear or
partial shearing. Replace any damaged components.
Tighten the flywheel nut to the proper torque.
3. Check for the correct air gap at the ignition modules.
An improper setting may cause contact between the
flywheel and laminations.
4. Remove the cylinder heads and check for excessive
carbon in the combustion chamber. Also check that
the head gasket fit is correct laying it over the cylinder
not the head. Check the spark plugs for proper reach
and heat range.
5. Check for proper valve lash.
6. Check internal components (pistons, cylinder bore,
connecting rods and crankshaft) for wear or damage.
ENGINE OVERHEATS
Before checking any of the following remove and inspect
the spark plugs one at a time. By reading the color of
each plug you can quickly narrow down which cylinder
is causing the problem. Spark plug color evaluation charts
can usually be found in spark plug manufacturer books.
1. Make sure the engine is not being overloaded.
Remove excessive loads by limiting operation speed,
processing less material.
2. Check the oil level and viscosity. Add or replace as
necessary.
3. Check for clogged cooling fins or obstructions to the
airflow. Remove the blower housing and clean the
cooling fins.
4. Check the carburetor for restricted metering jets,
causing a lean fuel delivery. Remove and clean the
carburetor using tag wire and compressed air. See
Chapter 3 under “Service.”
5. Check the engine R.P.M. setting using a vibra tach
or other tachometer. Compare it to the R.P.M.
settings found on microfiche card #30 or the
computer Parts Look Up system.
6. Check the ignition system. Check the CDI module
air gap and flywheel key condition.
7. Remove the cylinder head to check for excessive
carbon buildup or a leaking head gasket(s). Replace
head gasket(s).
8. Check for the correct spark plug and heat range.
Consult the parts look-up systems for the correct
plug.
SURGES OR RUNS UNEVENLY
1. Check the fuel cap for proper venting. Loosen the
cap and retry engine operation.
2. Replace or clean the air filter(s).
3. Static Test the Governor system.
4. Visually check all linkages. Check the governor shaft,
throttle link or link connector bushings for wear or
binding. For adjustment see Chapter 4.
5. Check the condition of the carburetor jets and
passages. Service as outlined in Chapter 3.
6. Verify engine R.P.M. setting using a vibra tach or
other tachometer. Compare it to the R.P.M. settings
found on microfiche card # 30. Adjust as necessary.
7. Check the ignition system operation using a gap type
tester installed between the high-tension lead and
spark plug. Check for intermittent spark.
ENGINE MISFIRES
1. Check the spark plugs for the proper reach and heat
range. Diagnose their condition. Replace if
questionable.
2. Replace the fuel and fuel filter if the condition is in
question. Set up a remote fuel tank to supply known
good fuel on a temporary basis. Test engine
performance.
NOTE: Questionable fuel should always be disposed
of properly. Contact your local governing body
regarding disposal options in your area.
3. Temporarily isolate the engine ground wires from
safety system. Check the ignition system with an in-
line ignition tester.
4. Check for carbon buildup in the combustion chamber.
5. Check valve lash. Inspect the valves and valve seats
for leakage. Check for scoring or discoloration on
the valve stem in the valve guides area. Recondition
the valves and seats if questionable.
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