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:
Removing the rear brake caliper
NOTE:
Before disassembling the brake caliper, drain
the brake fluid from the entire brake system.
1. Remove:
Union bolt "1"
Copper washers "2"
Brake hose "3"
NOTE:
Put the end of the brake hose into a container
and pump out the brake fluid carefully. ...
Checking the switches
1. Clutch switch
2. Main switch
3. Front brake light switch
4. Sidestand switch
5. Rear brake light switch
6. Neutral switch
7. Turn signal switch
8. Horn switch
9. Dimmer switch
10.Pass switch
11.Engine stop switch
12.Start switch
Check each switch for continuity with the pocket tes ...
Checking the front and rear brake pads
The front and rear brake pads must be
checked for wear at the intervals specified
in the periodic maintenance and
lubrication chart.
Front brake pads
Remove the front brake caliper by
removing the bolts.
Bolt
Brake caliper
Lining thickness
Check each front br ...