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:

    Checking the tires
    The following procedure applies to both of the tires. 1. Check: Tire pressure Out of specification Regulate. WARNING The tire pressure should only be checked and regulated when the tire temperature equals the ambient air temperature. The tire pressure must be adjuste ...

    Adjusting the brake pedal free play
    Adjusting the brake pedal free play Brake pedal free play The brake pedal free play should measure 3.5-4.5 mm (0.14-0.18 in) as shown. Periodically check the brake pedal free play and, if necessary, have a Yamaha dealer adjust it. WARNING An incorrect brake pedal free play in ...

    Checking the rear shock absorber assembly
    1. Check: Rear shock absorber rod Bends/damage Replace the rear shock absorber assembly. Rear shock absorber Oil leaks Replace the rear shock absorber assembly. Spring Damage/wear   Replace the rear shock absorber assembly. Bushing Damage/wear Replace the rea ...

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