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ENGINE

Starter Motor Does Not Operate or Does Not Turn Engine Over

1. Ignition switch not in ON position.
2. Engine run switch in OFF position.
3. Discharged battery, loose or corroded connections (solenoid chatters).
4. Starter control circuit, relay, or solenoid faulty.
5. Electric starter shaft pinion gear not engaging or overrunning clutch slipping.
6. Bank Angle Sensor tripped and ignition switch not cycled OFF then ON.

Engine Turns Over But Does Not Start

1. Fuel tank empty or fuel supply valve turned off.
2. Fouled spark plugs.
3. Engine flooded with gasoline as a result of over use of enrichener.
4. Vacuum hose to automatic fuel supply valve disconnected, leaking, or pinched.
5. Discharged battery, loose or broken battery terminal connections.
6. Engine lubricant too heavy (winter operation).
7. Spark plug cables in bad condition and shorting, cable connections loose or cables connected to incorrect cylinders.
8. Loose wire connection at coil, battery, ECM connector or ignition control module connector.
9. Ignition timing incorrect due to faulty coil, ECM, ignition control module or sensors.

Starts Hard

1. Spark plugs in bad condition or have improper gap or are partially fouled.
2. Spark plug cables in bad condition.
3. Battery nearly discharged.
4. Loose wire connection at one of the battery terminals, coil, ECM connector or ignition control module connector.
5. Carburetor controls not adjusted correctly.
6. Water or dirt in fuel system and carburetor.
7. Intake air leak.
8. Fuel tank vent hose and vapor valve plugged, or carburetor fuel line closed off, restricting fuel flow.
9. Enrichener valve inoperative.
10. Engine lubricant too heavy (winter operation).
11. Ignition not functioning properly (possible sensor failure).
12. Faulty ignition coil.
13. Valves sticking.

Starts But Runs Irregularly or Misses

1. Spark plugs in bad condition or partially fouled.
2. Spark plug cables in bad condition and leaking.
3. Spark plug gap too close or too wide.
4. Faulty ignition coil, module, or sensor.
5. Battery nearly discharged.
6. Damaged wire or loose connection at battery terminals, coil, ECM connector or ignition control module connector.
7. Intermittent short circuit due to damaged wire insulation.
8. Water or dirt in fuel system, carburetor or filter.
9. Fuel tank vent system plugged or carburetor vent line closed off.
10. Carburetor controls misadjusted.
11. Air leak at intake manifold or air cleaner.
12. Damaged carburetor.
13. Loose or dirty ECM connector or ignition control module connector.
14. Faulty Sensor(s): Manifold Absolute Pressure (MAP) and/or Crank Position (CKP).
15. Incorrect valve timing.
16. Weak or broken valve springs.
17. Damaged intake or exhaust valve.

A Spark Plug Fouls Repeatedly

1. Fuel mixture too rich or enrichener left on too long.
2. Incorrect spark plug for the kind of service.
3. Piston rings badly worn or broken.
4. Valve guides or seals badly worn. Pre-Ignition or Detonation (Knocks or Pings)
1. Fuel octane rating too low.
2. Faulty spark plugs.
3. Incorrect spark plug for the kind of service.
4. Excessive carbon deposit on piston head or in combustion chamber.
5. Ignition timing advanced due to faulty sensor inputs (MAP and/or CKP).

Overheating

1. Insufficient oil supply or oil not circulating.
2. Insufficient air flow over engine.
3. Heavy carbon deposit.
4. Ignition timing retarded due to faulty sensor(s): Manifold Absolute Pressure (MAP) and/or Crank Position (CKP).
5. Leaking valve.

Valve Train Noise

1. Low oil pressure caused by oil feed pump not functioning properly or oil passages obstructed.
2. Faulty hydraulic lifters.
3. Bent push rod.
4. Incorrect push rod length.
5. Rocker arm binding on shaft.
6. Valve sticking in guide.
7. Chain tensioning spring or shoe worn.

Excessive Vibration

1. Wheels and/or tires worn or damaged.
2. Engine/transmission/rear wheel not aligned properly.
3. Primary chain badly worn or links tight as a result of insufficient lubrication or misalignment.
4. Engine to transmission mounting bolts loose.
5. Upper engine mounting bracket loose.
6. Ignition timing advanced due to faulty sensor inputs (MAP and/or CKP)/poorly tuned engine.
7. Internal engine problem.
8. Broken frame.

Check Engine Light Illuminates During Operation

1. Fault detected.

Oil Does Not Return To Oil Pan

1. Oil pan empty.
2. Oil pump not functioning.
3. Restricted oil lines or fittings.
4. Restricted oil filter.
5. Oil pump misaligned or in poor condition.
6. O-ring damaged or missing from oil pump/crankcase junction (also results in poor engine performance).

Engine Uses Too Much Oil Or Smokes Excessively

1. Oil pan overfilled.
2. Restricted oil return line to pan.
3. Restricted breather operation.
4. Restricted oil filter.
5. Oil pump misaligned or in poor condition.
6. Piston rings badly worn or broken.
7. Valve guides or seals worn.
8. O-ring damaged or missing from oil pump/crankcase junction (also results in poor engine performance).
9. Plugged crankcase scavenge port.

Engine Leaks Oil From Cases, Push Rods, Hoses, Etc.

1. Loose parts.
2. Imperfect seal at gaskets, push rod cover, washers, etc.
3. Restricted breather hose to air cleaner.
4. Restricted oil filter.
5. Oil pan overfilled.
6. Lower rocker housing gasket installed incorrectly (upside down).
7. Restricted oil return line to tank.

Low Oil Pressure

1. Oil pan underfilled.
2. Faulty low oil pressure switch.
3. Oil pump O-ring damaged or missing.
4. Bypass valve stuck in open position.
5. Ball or clean-out plug missing or leaking in cam support plate.
6. O-ring missing from cam support plate.

High Oil Pressure

1. Oil pan overfilled.
2. Bypass valve stuck in closed position.