TROUBLESHOOTING
9-2
• Flooded throttle body
• Faulty air induction system
Electrical system
1. Battery
• Discharged battery
• Faulty battery
2. 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
3. Ignition coil
• Broken or shorted primary or secondary coils
• Faulty spark plug lead
• Cracked or broken ignition coil
4. Ignition system
• Faulty ECU
• Faulty crankshaft position sensor
• Broken generator rotor woodruff key
EAS28510
POOR MEDIUM-AND-HIGH-SPEED
PERFORMANCE
Refer to “STARTING FAILURES” on page 9-1.
Engine
1. Air filter
• Clogged air filter element
Fuel system
1. Fuel pump
• Faulty fuel pump
EAS28530
FAULTY GEAR SHIFTING
Shifting is difficult
Refer to “Clutch drags”.
EAS28540
SHIFT PEDAL DOES NOT MOVE
Shift shaft
• Improperly adjusted shift rod
• Bent shift shaft
Shift drum and shift forks
• Foreign object in a shift drum groove
• Seized shift fork
• Bent shift fork guide bar
Transmission
• Seized transmission gear
• Foreign object between transmission gears
• Improperly assembled transmission
EAS28550
JUMPS OUT OF GEAR
Shift shaft
• Incorrect shift pedal position
• Improperly returned stopper lever
Shift forks
• Worn shift fork
Shift drum
• Incorrect axial play
• Worn shift drum groove
Transmission
• Worn gear dog
EAS28560
FAULTY CLUTCH
Clutch slips
1. Clutch
• Improperly assembled clutch
• Improperly adjusted clutch cable
• Loose or fatigued clutch spring
• Worn friction plate
• Worn clutch plate
2. Engine oil
• Incorrect oil level
• Incorrect oil viscosity (low)
• Deteriorated oil
Clutch drags
1. Clutch
• Unevenly tensioned clutch springs
• Warped pressure plate
• Bent clutch plate
• Swollen friction plate
• Bent clutch push rod
• Broken clutch boss
• Burnt primary driven gear bushing
2. Engine oil
• Incorrect oil level
• Incorrect oil viscosity (high)
• Deteriorated oil
EAS28600
OVERHEATING
Engine
1. Clogged coolant passages
• Cylinder head and piston
• Heavy carbon buildup
YamahaR125.COM
Summary of Contents for YZF-R125
Page 1: ...5D7 F8197 E0 YAMAHAR125 COM SERVICE MANUAL YZF R125 ...
Page 6: ...YamahaR125 COM ...
Page 8: ...YamahaR125 COM ...
Page 52: ...LUBRICATION SYSTEM CHART AND DIAGRAMS 2 29 1 2 3 4 YamahaR125 COM ...
Page 70: ...CABLE ROUTING 2 47 YamahaR125 COM ...
Page 73: ...YamahaR125 COM ...
Page 102: ...ELECTRICAL SYSTEM 3 29 YamahaR125 COM ...
Page 105: ...YamahaR125 COM ...
Page 172: ...CHAIN DRIVE 4 67 YamahaR125 COM ...
Page 181: ...ENGINE REMOVAL 5 6 2 2 4 1 3 YamahaR125 COM ...
Page 263: ...THROTTLE BODY 7 8 YamahaR125 COM ...
Page 264: ...AIR INDUCTION SYSTEM 7 9 EAS27040 AIR INDUCTION SYSTEM 1 2 3 YamahaR125 COM ...
Page 268: ...AIR INDUCTION SYSTEM 7 13 YamahaR125 COM ...
Page 271: ...YamahaR125 COM ...
Page 283: ...CHARGING SYSTEM 8 12 1 AC magneto 3 Rectifier regulator 4 Main fuse 9 Battery YamahaR125 COM ...
Page 285: ...CHARGING SYSTEM 8 14 YamahaR125 COM ...
Page 295: ...SIGNALING SYSTEM 8 24 YamahaR125 COM ...
Page 299: ...COOLING SYSTEM 8 28 YamahaR125 COM ...
Page 323: ...FUEL INJECTION SYSTEM 8 52 YamahaR125 COM ...
Page 327: ...FUEL PUMP SYSTEM 8 56 YamahaR125 COM ...
Page 353: ...YamahaR125 COM ...
Page 354: ...YamahaR125 COM ...