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:

    Protective apparel
    The majority of fatalities from motorcycle accidents are the result of head injuries. The use of a safety helmet is the single most critical factor in the prevention or reduction of head injuries. Always wear an approved helmet. Wear a face shield or goggles. Wind in your unprotecte ...

    Preparation for removal and disassembly
    1. Before removal and disassembly, remove all dirt, mud, dust and foreign material. 2. Use only the proper tools and cleaning equipment. Refer to "SPECIAL TOOLS" on page 1-8. 3. When disassembling, always keep mated parts together. This includes gears, cylinders, pistons and other part ...

    Installing the swingarm
    1. Lubricate: Bearings Spacers Dust covers Pivot shaft 2. Install: Bearings "1" 2. Swingarm A. Left side B. Right side 3. Install: Swingarm adjusting collar "1" Swingarm "2" Pivot shaft Pivot shaft nut "3" a. Install, and then fully turn in the swingarm adju ...

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