Tecumseh VLV Technician's Handbook page 37

Cause
ENGINE MISSES UNDER LOAD
Spark plug fouled
Spark plug porcelain cracked
Improper spark plug gap
Improper valve clearance
Weak valve spring
ENGINE LACKS POWER
Ignition improperly timed
Worn rings
Lack of lubrication
Air cleaner fouled
Valves leaking
ENGINE OVERHEATS
Engine improperly timed
Air flow obstructed
Cooling fins clogged
Excessive load on engine
Carbon in combustion chamber
Lack of lubrication
ENGINE SURGES OR RUNS UNEVENLY
Fuel tank cap vent hole clogged
Governor parts sticking or binding
Carburetor throttle linkage or throttle shaft
and/or butterfly binding or sticking
Intermittent spark at spark plug
Dirty carburetor
ENGINE VIBRATES EXCESSIVELY
Engine not securely mounted
Bent crankshaft
Associated equipment out of balance
34
4-CYCLE ENGINE TROUBLESHOOTING CHART (Cont.)
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Remedy and Reference
Replace spark plug.
Replace spark plug.
Regap spark plug.
Adjust valve clearance to recommended specifications.
Replace valve spring.
Replace flywheel key.
Replace rings.
Fill crankcase to the proper level.
Service air cleaner.
Grind valves and set to recommended specifications.
Replace flywheel key if sheared.
Remove any obstructions from air passages in shrouds.
Clean cooling fins.
Check operation of associated equipment. Reduce
excessive load.
Remove cylinder head and clean carbon from head and
piston.
Fill crankcase to proper level.
Open vent hole.
Clean, and if necessary repair governor parts.
Clean, lubricate, or adjust linkage and deburr throttle shaft
or butterfly.
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.
Clean carburetor.
Tighten loose mounting bolts.
Replace crankshaft.
Check associated equipment.