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:

Checking the front fork
1. Stand the vehicle on a level surface. WARNINGSecurely support the vehicle so that there is no danger of it falling over. 2. Check: Inner tube Damage/scratches Replace. Oil seal Oil leakage Replace. 3. Hold the vehicle upright and apply the front brake. 4. Che ...

Installing the camshaft and rocker arms
1. Lubricate: Rocker arms Rocker arm shafts 2. Lubricate: Camshaft 3. Install: Camshaft "1" NOTE: Make sure that the camshaft projections "a" and hole "b" are positioned as shown in the illustration. 4. Install: Rocker arms Rocker arm shafts "1" NOTE: Make ...

Checking the camshaft
1. Check: Camshaft lobes Blue discoloration/pitting/scratches Replace the camshaft. 2. Measure: Camshaft lobe dimensions "a" and "b" Out of specification Replace the camshaft. 3. Check: Camshaft oil passage Obstruction Blow out with compressed air. ...