Yamaha YZF-R125 Service Manual: Overheating

Yamaha YZF-R125 Service Manual / Troubleshooting / 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:

Assembling the oil pump
1. Lubricate: Oil pump inner rotor Oil pump outer rotor Oil pump driven gear (with the recommended lubricant) 2. Install: Oil pump outer rotor Oil pump inner rotor "1" Oil pump driven gear Pin "2" NOTE: When installing the inner rotor, align the pin "2" in the oil pump sh ...

Checking the rocker arms and rocker arm shafts
The following procedure applies to all of the rocker arms and rocker arm shafts. 1. Check: Rocker arm Damage/wear Replace. 2. Check: Rocker arm shaft Blue discoloration/excessive wear/pitting/ scratches Replace or check the lubrication system. 3. Measure: Rocke ...

Disassembling the front wheel
1. Remove: Oil seal Wheel bearings a. Clean the surface of the front wheel hub. b. Remove the oil seal "1" with a flat-head screwdriver. NOTE: To prevent damaging the wheel, place a rag "2" between the screwdriver and the wheel surface. c. Remove the wheel bearings "3" with a ge ...