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:
Adjusting the drive chain slack
NOTE:
The drive chain slack must be checked at the
tightest point on the chain.
CAUTION:A drive chain that is too tight will
overload
the engine and other vital parts, and one that
is too loose can skip and damage the swingarm
or cause an accident. Therefore, keep
the drive ...
Removing the generator
1. Remove:
Generator rotor nut "1"
Washer
NOTE:
While holding the generator rotor "2" with the
sheave holder "3", loosen the generator rotor
nut.
Do not allow the sheave holder to touch the
projection on the generator rotor.
2. Remove:
Generator rotor "1"
(with the ...
Checking the coolant temperature sensor
1. Remove:
Coolant temperature sensor
WARNING
Handle the coolant temperature sensor
with special care.
Never subject the coolant temperature sensor
to strong shocks. If the coolant temperature
sensor is dropped, replace it.
2. Check:
Coolant temper ...