Yamaha V Star 950 Service Manual page 382

EAS28450
TROUBLESHOOTING
EAS28460
GENERAL INFORMATION
TIP
The following guide for troubleshooting does
not cover all the possible causes of trouble. It
should be helpful, however, as a guide to basic
troubleshooting. Refer to the relative proce-
dure in this manual for checks, adjustments,
and replacement of parts.
EAS28470
STARTING FAILURES
Engine
1. Cylinder(s) and cylinder head(s)
• Loose spark plug
• Loose cylinder head or cylinder
• Damaged cylinder head gasket
• Damaged cylinder gasket
• Worn or damaged cylinder
• Incorrect valve clearance
• Improperly sealed valve
• Incorrect valve-to-valve-seat contact
• Incorrect valve timing
• Faulty valve spring
• Seized valve
2. Piston(s) and piston ring(s)
• Improperly installed piston ring
• Damaged, worn or fatigued piston ring
• Seized piston ring
• Seized or damaged piston
3. Air filter
• Improperly installed air filter
• Clogged air filter element
4. Crankcase and crankshaft
• Improperly assembled crankcase
• Seized crankshaft
Fuel system
1. Fuel tank
• Empty fuel tank
• Clogged fuel filter
• Clogged fuel tank breather hose
• Clogged rollover valve
• Deteriorated or contaminated fuel
2. Fuel pump
• Faulty fuel pump
• Faulty relay unit (fuel pump relay)
3. Throttle body(-ies)
• Deteriorated or contaminated fuel
• Sucked-in air
TROUBLESHOOTING
Electrical system
1. Battery
• Discharged battery
• Faulty battery
2. Fuse(s)
• Blown, damaged or incorrect fuse
• Improperly installed fuse
3. Spark plug(s)
• Incorrect spark plug gap
• Incorrect spark plug heat range
• Fouled spark plug
• Worn or damaged electrode
• Worn or damaged insulator
• Faulty spark plug cap
4. Ignition coil(s)
• Cracked or broken ignition coil body
• Broken or shorted primary or secondary
coils
• Faulty spark plug lead
5. Ignition system
• Faulty ECU
• Faulty crankshaft position sensor
• Broken generator rotor Woodruff key
6. Switches and wiring
• Faulty main switch
• Faulty engine stop switch
• Broken or shorted wiring
• Faulty neutral switch
• Faulty start switch
• Faulty sidestand switch
• Faulty clutch switch
• Improperly grounded circuit
• Loose connections
7. Starting system
• Faulty starter motor
• Faulty starter relay
• Faulty relay unit (starting circuit cut-off
relay)
• Faulty starter clutch
EAS28490
INCORRECT ENGINE IDLING SPEED
Engine
1. Cylinder(s) and cylinder head(s)
• Incorrect valve clearance
• Damaged valve train components
2. Air filter
• Clogged air filter element
Fuel system
1. Throttle body(-ies)
• Damaged or loose throttle body joint
• Improperly synchronized throttle bodies
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