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:
Checking the water pump
1. Check:
Water pump housing cover
Water pump housing
Cracks/damage Replace.
Impeller shaft
Cracks/damage/wear Replace.
Bearing
Rough movement Replace.
Radiator outlet hose
Cracks/damage Replace.
...
Checking the clutch housing
1. Check:
Clutch housing dogs "1"
Damage/pitting/wear
Deburr the clutch
housing dogs or replace the clutch housing.
NOTE:
Pitting on the clutch housing dogs will cause erratic
clutch operation.
2. Check:
Bearing
Damage/wear Replace the
bearing and
clutch housin ...
Checking the condition of the bulbs
The following procedure applies to all of the
bulbs.
1. Remove:
Bulb
WARNINGSince the headlight bulbs get extremely
hot,
keep flammable products and your hands
away from them until they have cooled
down.
CAUTION:
Be sure to hold the socket firmly when re ...