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 throttle body joint and air filter case joint
1. Remove:
Right lower side cowling
Left lower side cowling
Refer to "GENERAL CHASSIS" on page 4-1.
2. Check:
Throttle body joint "1"
Air filter case joint "2"
Cracks/damage Replace.
3. Install:
Right lower side cowling
Left lower side cowling
Refer to "GENERAL CHAS ...
Checking the condition of the bulbs
The following procedure applies to all of the
bulbs.
1. Remove:
Bulb
WARNINGSince the headlight bulbs get extremely
hot,
keep flammable products and your hands
away from them until they have cooled
down.
CAUTION:
Be sure to hold the socket firmly when re ...
General maintenance and lubrication chart
TIP
The air filter needs more frequent service if you are riding in
unusually wet or dusty areas.
Hydraulic brake service
Regularly check and, if necessary, correct the brake fluid level.
Every two years change the brake fluid.
Replace the brake hoses every four ye ...