3.59
ENGINE
3
Excessive Smoke and Carbon Buildup
• Excessive piston-to-cylinder clearance
• Wet sumping due to over-full crankcase
• Worn rings, piston, or cylinder
• Worn valve guides or seals
• Restricted breather
• Air filter dirty or contaminated
Low Compression
• Cylinder head gasket leak
• No valve clearance ( cam wear )
• Cylinder or piston worn
• Piston rings worn, leaking, broken, or sticking
• Bent valve or stuck valve
• Valve spring broken or weak
• Valve not seating properly (bent or carbon accumulated
on sealing surface)
• Rocker arm sticking
Backfiring
• ETC or speed limiter system malfunction
• Fouled spark plug or incorrect plug or plug gap
• Exhaust system air leaks
• Exhaust system air leaks
• Ignition system faulty:
Spark plug cap cracked / broken
Ignition coil faulty
Ignition or kill switch circuit faulty
Poor connections in ignition system
Ignition timing incorrect
Sheared flywheel key
• Valve sticking
Cooling System
Overheating
• Low coolant level
• Air in cooling system
• Wrong type/mix of coolant
• Faulty pressure cap or system leaks
• Restricted system (mud or debris in radiator fins
causing restriction to air flow, passages blocked in
radiator, lines, pump, or water jacket, accident damage)
• Lean mixture (restricted jets, vents, fuel pump or fuel
valve)
• Fuel pump output weak
• Electrical malfunction
• Water pump failure/ Loose impeller
• Thermistor failure
• Cooling fan inoperative or turning too slowly (perform
current draw test)
• Ignition timing mis-adjusted
• Low oil level
• Spark plug incorrect heat range
• Faulty hot light circuit
• Thermostat stuck closed or not opening completely
Temperature Too Low
• Thermostat stuck open
Leak at Water Pump Weep Hole
• Faulty water pump mechanical seal (coolant leak)
• Faulty pump shaft oil seal (oil leak)
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