TROUBLESHOOTING
9-1
EASB291369
TROUBLESHOOTING
EASB291370
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 procedure
in this manual for checks, adjustments, and re-
placement of parts.
EASB291371
STARTING FAILURES
Engine
1. Cylinder and cylinder head
• 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 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 tank breather hose
• Deteriorated or contaminated fuel
• Clogged or damaged fuel hose
2. Fuel pump
• Faulty fuel pump
3. Throttle body
• Deteriorated or contaminated fuel
• Sucked-in air
Electrical system
1. Spark plug
• Incorrect spark plug gap
• Incorrect spark plug heat range
• Fouled spark plug
• Worn or damaged electrode
• Worn or damaged insulator
2. Ignition coil
• Cracked or broken ignition coil body
• Broken or shorted primary or secondary
coils
3. Ignition system
• Faulty ECU
• Faulty crankshaft position sensor
• Broken generator rotor woodruff key
4. Switches and wiring
• Faulty ECU
• Faulty engine stop switch
• Broken or shorted wiring
• Faulty neutral switch
• Improperly grounded circuit
• Loose connections
EASB291372
INCORRECT ENGINE IDLING SPEED
Engine
1. Cylinder and cylinder head
• Incorrect valve clearance
• Damaged valve train components
2. Air filter
• Clogged air filter element
Fuel system
1. Throttle body
• Damaged or loose throttle body joint
• Improperly synchronized throttle bodies
• Improper throttle cable free play
• Flooded throttle body
Electrical system
1. Spark plug
• Incorrect spark plug gap
• Incorrect spark plug heat range
• Fouled spark plug
• Worn or damaged electrode
• Worn or damaged insulator
• Faulty spark plug cap
2. Ignition coil
• Broken or shorted primary or secondary
coils
• Cracked or broken ignition coil
3. Ignition system
• Faulty ECU
• Faulty crankshaft position sensor
• Broken generator rotor woodruff key
Summary of Contents for YZ 2015 Series
Page 6: ...EASB291006 YAMAHA MOTOR CORPORATION U S A YZ MOTORCYCLE LIMITED WARRANTY...
Page 10: ......
Page 33: ...CONTROL FUNCTIONS 1 21 a 2...
Page 65: ...LUBRICATION POINTS AND LUBRICANT TYPES 2 22 EASB291066...
Page 68: ...LUBRICATION SYSTEM CHART AND DIAGRAMS 2 25...
Page 70: ...LUBRICATION SYSTEM CHART AND DIAGRAMS 2 27...
Page 72: ...LUBRICATION SYSTEM CHART AND DIAGRAMS 2 29...
Page 74: ...CABLE ROUTING DIAGRAM 2 31 EASB291068 CABLE ROUTING DIAGRAM...
Page 76: ...CABLE ROUTING DIAGRAM 2 33...
Page 78: ...CABLE ROUTING DIAGRAM 2 35...
Page 80: ...CABLE ROUTING DIAGRAM 2 37...
Page 82: ...CABLE ROUTING DIAGRAM 2 39...
Page 84: ...CABLE ROUTING DIAGRAM 2 41...
Page 86: ...CABLE ROUTING DIAGRAM 2 43...
Page 88: ...CABLE ROUTING DIAGRAM 2 45...
Page 128: ...ELECTRICAL SYSTEM 3 38...
Page 200: ...CHAIN DRIVE 4 70...
Page 244: ...ELECTRIC STARTER 5 41...
Page 266: ...OIL PUMP AND BALANCER GEAR 5 63 c d 6 6 7 8 8 b...
Page 286: ...TRANSMISSION 5 83...
Page 306: ...CHECKING THE INTAKE AIR TEMPERATURE SENSOR 8 67 CHECKING THE FUEL INJECTOR 8 68...
Page 321: ...CHARGING SYSTEM 8 15 EASB291338...
Page 325: ...COOLING SYSTEM For JPN 8 19 EASB291341...
Page 355: ...FUEL PUMP SYSTEM 8 49 EASB291348...
Page 356: ...ELECTRICAL COMPONENTS 8 50 ELECTRICAL COMPONENTS EASB291349 8 9 10 1 3 2 4 5 6 7...
Page 358: ...ELECTRICAL COMPONENTS 8 52 11 10 9 2 3 1 6 7 8 4 5...
Page 360: ...ELECTRICAL COMPONENTS 8 54 EASB291350 CHECKING THE SWITCHES 4 1 3 2 E B S E B E B E E B B...
Page 382: ...LIST OF SELF DIAGNOSTIC AND FAIL SAFE ACTIONS 9 7...