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 cylinder head
1. Eliminate: Combustion chamber carbon deposits (with a rounded scraper) NOTE: Do not use a sharp instrument to avoid damaging or scratching: Spark plug bore threads Valve seats 2. Check: Cylinder head Damage/scratches Replace. Cylinder head water jacket Min ...

Checking the rear brake master cylinder
1. Check: Brake master cylinder Damage/scratches/wear Replace. Brake fluid delivery passages (brake master cylinder body) Obstruction Blow out with compressed air. 2. Check: Brake master cylinder kit Damage/scratches/wear Replace. 3. Check: Brake fluid reservoir Cracks/ ...

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 ...