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:

    Circuit diagram
    4. Main fuse 5. Main switch 9. Battery 25.ECU (engine control unit) 36.License plate light 37.Tail/brake light 44.Headlight relay 46.Pass switch 47.Dimmer switch 51.Headlight (low beam) 52.Auxiliary light 54.Headlight (high beam) 58.Meter light 60.High beam indicator light 64.Ignit ...

    Checking the front brake caliper
    1. Check: Brake caliper pistons "1" Rust/scratches/wear Replace the brake caliper assembly. Brake caliper body "2" Cracks/damage Replace the brake caliper assembly. Brake fluid delivery passages (brake caliper body) Obstruction Blow out with compressed air. ...

    Adjusting the rear disc brake
    1. Check: Brake pedal position (distance "a" from the center of the rider footrest to the center of the brake pedal) Out of specification Adjust. 2. Adjust: Brake pedal position a. Loosen the locknut "1". b. Remove the cotter pin "2", washer "3", and pin "4". c. Turn t ...

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