Yamaha YZF-R125 Service Manual: 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.

Checking the piston pin


3. Measure:

  • Piston pin bore diameter "b" Out of specification Replace
    the piston.

Checking the piston pin


4. Calculate:

Piston-pin-to-piston-pin-bore clearance Out of specification Replace the
piston pin and piston as a set.

  • Piston-pin-to-piston-pin-bore clearance = Piston pin bore diameter "b" - Piston pin outside diameter "a"

    Checking the piston rings
    1. Measure: Piston ring side clearance Out of specification Replace the piston and piston rings as a set. NOTE: Before measuring the piston ring side clearance, eliminate any carbon deposits ...

    Installing the piston and cylinder
    1. Install: Top ring "1" 2nd ring "2" Oil ring expander "3" Lower oil ring rail "4" Upper oil ring rail "5" NOTE: Be sure to install the piston rings so that the manufacturer marks or ...

    Other materials:

    Removing the lower bracket
    1. Stand the vehicle on a level surface. WARNINGSecurely support the vehicle so that there is no danger of it falling over. 2. Remove: Upper ring nut Rubber washer Lower ring nut "1" Lower bracket NOTE: Remove the lower ring nut with the steering nut wrench "2". ...

    Bearings and oil seals
    Install bearings "1" and oil seals "2" so that the manufacturer's marks or numbers are visible. When installing oil seals "1", lubricate the oil seal lips with a light coat of lithium-soap-based grease. Oil bearings liberally when installing, if appropriate. CAUTION:Do not spin th ...

    Installing the radiator
    1. Fill: Cooling system (with the specified amount of the recommended coolant) Refer to "CHANGING THE COOLANT" on page 3-15. 2. Check: Cooling system Leaks Repair or replace any faulty part. 3. Measure: Radiator cap opening pressure Below the specified pressure Repla ...

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