Yamaha YZF-R125 Service Manual: Overheating

Engine

1. Clogged coolant passages

  • Cylinder head and piston
  • Heavy carbon buildup

2. Engine oil

  • Incorrect oil level
  • Incorrect oil viscosity
  • Inferior oil quality

Cooling system

1. Coolant

  • Low coolant level

2. Radiator

  • Damaged or leaking radiator
  • Faulty radiator cap
  • Bent or damaged radiator fin

3. Water pump

  • Damaged or faulty water pump
  • Thermostat
  • Thermostat stays closed
  • Hose(s) and pipe(s)
  • Damaged hose
  • Improperly connected hose
  • Damaged pipe
  • Improperly connected pipe

Fuel system

1. Throttle body

  • Damaged or loose throttle body joint

2. Air filter

  • Clogged air filter element

Chassis

1. Brake(s)

  • Dragging brake

Electrical system

1. Spark plug

  • Incorrect spark plug gap
  • Incorrect spark plug heat range

2. Ignition system

  • Faulty ECU

Overcooling

Cooling system

1. Thermostat

  • Thermostat stays open
    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 oi ...

    Poor braking performance
    - Worn brake pad - Worn brake disc - Air in hydraulic brake system - Leaking brake fluid - Faulty brake caliper kit - Faulty brake caliper seal - Loose union bolt - Damaged brake hose - Oil or ...

    Other materials:

    Safe Riding
    Perform the pre-operation checks each time you use the vehicle to make sure it is in safe operating condition. Failure to inspect or maintain the vehicle properly increases the possibility of an accident or equipment damage. See page 4-1 for a list of pre-operation checks. This motor ...

    Adjusting the engine idling speed
    NOTE: Prior to adjusting the engine idling speed, the air filter element should be clean, and the engine should have adequate compression. 1. Start the engine and let it warm up for several minutes. 2. Remove: Rider seat Refer to "GENERAL CHASSIS" on page 4-1. 3. Lift the fuel tank. ...

    Checking the connections
    Check the leads, couplers, and connectors for stains, rust, moisture, etc. 1. Disconnect: Lead Coupler Connector 2. Check: Lead Coupler Connector Moisture → Dry with an air blower. Rust/stains → Connect and disconnect several times. 3. Check: All co ...

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