Yamaha YZF-R125 Service Manual: Incorrect engine idling speed

Yamaha YZF-R125 Service Manual / Troubleshooting / 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:

    Adjusting the rear disc brake
    1. Check: Brake pedal position (distance "a" from the center of the rider footrest to the center of the brake pedal) Out of specification Adjust. 2. Adjust: Brake pedal position a. Loosen the locknut "1". b. Remove the cotter pin "2", washer "3", and pin "4". c. Turn t ...

    Setting the diagnostic mode
    1. Set the main switch to "OFF" and the engine stop switch to " ". 2. Disconnect the self-diagnosis signal connector "1", and then connect the FI diagnostic tool "2" as shown. 3. Disconnect the fuel pump coupler. 4. While pressing the "MODE" button, set the main switch to "ON". NOTE: ...

    Installing the cylinder head
    1. Install: Cylinder head NOTE: Pass the timing chain through the timing chain cavity. 2. Tighten: Cylinder head bolts "1" Cylinder head bolts "2" NOTE: Lubricate the cylinder head bolts and washers with engine oil. Tighten the cylinder head bolts in the proper tighten ...

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