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:

    Installing the clutch
    1. Install: Conical spring washer "1" NOTE: Install the conical spring washer as shown in the illustration. 2. Install: Clutch housing Thrust washer "1" NOTE: Be sure to install the thrust washer so that its sharp edge "a" is facing away from the clutch boss. 3. Instal ...

    VInstalling the handlebars
    1. Stand the vehicle on a level surface. WARNINGSecurely support the vehicle so that there is no danger of it falling over. 2. Install: Front brake master cylinder "1" Front brake master cylinder holder "2" Front brake light switch NOTE: Install the brake master cyl ...

    Installing the rear shock absorber assembly
    1. Install: Rear shock absorber assembly Relay arm "1" NOTE: Install the relay arm as shown in the illustration. 2. Tighten: Rear shock absorber assembly upper nut Relay arm nut Rear shock absorber assembly lower nut 3. Install: Connecting arms NOTE: When ins ...

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