Yamaha YZF-R125 Service Manual: Checking the thermostat

1. Check:

  • Thermostat Does not open at 80.5-83.5 C (176.9-182.3 F)  Replace.

a. Suspend the thermostat "1" in a container "2" filled with water.

b. Slowly heat the water "3".

c. Place a thermometer "4" in the water.

d. While stirring the water, observe the thermostat and thermometer's indicated temperature.

Checking the thermostat


A. Fully closed

B. Fully open

NOTE:

If the accuracy of the thermostat is in doubt, replace it. A faulty thermostat could cause serious overheating or overcooling.

2. Check:

  • Thermostat cover Cracks/damage Replace.

3. Check:

  • Radiator inlet hose Cracks/damage  Replace.

    Thermostat
    ...

    Installing the thermostat
    1. Install: Thermostat NOTE: Install the thermostat with its breather hole "a" facing up. 2. Install: Copper washer Coolant temperature sensor CAUTION:Use extreme care when ...

    Other materials:

    Checking the valves and valve guides
    The following procedure applies to all of the valves and valve guides. 1. Measure: Valve-stem-to-valve-guide clearance Out of specification Replace the valve guide. Valve-stem-to-valve-guide clearance = Valve guide inside diameter "a" - Valve stem diameter "b" 2. Replace: ...

    Checking the piston pin
    1. Check: Piston pin Blue discoloration/grooves  Replace the piston pin and then check the lubrication system. 2. Measure: Piston pin outside diameter "a" Out of specification Replace the piston pin. 3. Measure: Piston pin bore diameter "b" Out of specifica ...

    Checking the starter clutch
    1. Check: Starter clutch rollers "1" Starter clutch spring caps "2" Starter clutch springs "3" Damage/wear Replace the starter clutch assembly. 2. Check: Starter clutch idle gear Starter clutch gear Burrs/chips/roughness/wear Replace the defective part(s). 3. Check: ...

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