Yamaha YZF-R125 Service Manual: 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 adjusted engine idling speed (idle adjusting screw)
- Improper throttle cable free play
- 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
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 c ...
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
Faulty gear shifting
Shifting is difficult
Refer ...
Other materials:
Troubleshooting charts
Starting problems or poor engine performance
Starting problems or poor engine performance
Engine overheating
WARNING
Do not remove the radiator cap when the engine and radiator are hot.
Scalding hot fluid and steam may be
blown out under pressure, which could cause serious injury. Be ...
Checking the transmission
1. Measure:
Main axle runout
(with a centering device and dial gauge "1")
Out of specification Replace
the main axle.
2. Measure:
Drive axle runout
(with a centering device and dial gauge "1")
Out of specification Replace
the drive axle.
3. Check:
Transmiss ...
Shifting
Shifting
Shift pedal
Neutral position
Shifting gears lets you control the
amount of engine power available for
starting off, accelerating, climbing hills,
etc.
The gear positions are shown in the illustration.
TIP
To shift the transmission into the neutral
position, press the ...