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4-CYCLE ENGINE TROUBLESHOOTING CHART (Cont.)
Cause Remedy and Reference
ENGINE MISSES UNDER LOAD
Spark plug fouled Replace spark plug.
Spark plug porcelain cracked Replace spark plug.
Improper spark plug gap Regap spark plug.
Improper valve clearance Adjust valve clearance to recommended specifications.
Weak valve spring Replace valve spring.
ENGINE LACKS POWER
Ignition improperly timed Replace flywheel key.
Worn rings Replace rings.
Lack of lubrication Fill crankcase to the proper level.
Air cleaner fouled Service air cleaner.
Valves leaking Grind valves and set to recommended specifications.
ENGINE OVERHEATS
Engine improperly timed Replace flywheel key if sheared.
Air flow obstructed Remove any obstructions from air passages in shrouds.
Cooling fins clogged Clean cooling fins.
Excessive load on engine Check operation of associated equipment. Reduce
excessive load.
Carbon in combustion chamber Remove cylinder head and clean carbon from head and
piston.
Lack of lubrication Fill crankcase to proper level.
ENGINE SURGES OR RUNS UNEVENLY
Fuel tank cap vent hole clogged Open vent hole.
Governor parts sticking or binding Clean, and if necessary repair governor parts.
Carburetor throttle linkage or throttle shaft Clean, lubricate, or adjust linkage and deburr throttle shaft
and/or butterfly binding or sticking or butterfly.
Intermittent spark at spark plug Disconnect ignition cut-off wire at the engine. Crank
engine. If spark, check ignition switch, safety switch and
interlock switch. If no spark, check ignition air gap. Check
wires for poor connections, cuts or breaks.
Dirty carburetor Clean carburetor.
ENGINE VIBRATES EXCESSIVELY
Engine not securely mounted Tighten loose mounting bolts.
Bent crankshaft Replace crankshaft.
Associated equipment out of balance Check associated equipment.
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