Yamaha YZF-R125 Service Manual: Installing the piston and cylinder

Yamaha YZF-R125 Service Manual / Engine / Cylinder and piston / 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 numbers face up.

Installing the piston and cylinder


2. Install:

  • Piston "1"
  • Piston pin "2"
  • Piston pin clips "3"

NOTE:

  • Apply engine oil to the piston pin.
  • Make sure the arrow mark "a" on the piston points towards the exhaust side of the cylinder.
  • Before installing the piston pin clips, cover the crankcase opening with a clean rag to prevent the clips from falling into the crankcase.

Installing the piston and cylinder


3. Lubricate:

  • Piston
  • Piston rings
  • Cylinder (with the recommended lubricant)

4. Offset:

  • Piston ring end gaps

a. Top ring

b. Upper oil ring rail

c. Oil ring expander

d. Lower oil ring rail

e. 2nd ring

f. 20 mm (0.79 in)

A. Intake side

5. Install:

  • Dowel pins
  • Cylinder head gasket

  • Cylinder "1"

NOTE:

  • While compressing the piston rings with one hand, install the cylinder with the other hand.
  • Pass the timing chain and timing chain guide (intake side) through the timing chain cavity.

Installing the piston and cylinder


    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 ...

    Generator and starter clutch
    ...

    Other materials:

    Checking the timing chain tensioner
    1. Check: Timing chain tensioner Cracks/damage/rough movement Replace. a. Lightly press the timing chain tensioner rod into the timing chain tensioner housing by hand. NOTE: While pressing the timing chain tensioner rod, wind it clockwise with a thin screwdriver "1" until it stops. b. ...

    Checking the drive sprocket
    1. Check: Drive sprocket More than 1/4 tooth "a" wear Replace the drive chain sprockets as a set. Bent teeth Replace the drive chain sprockets as a set. b. Correct 1. Drive chain roller 2. Drive chain sprocket Checking the rear wheel sprocket Refer to "CHECKING AND R ...

    Removing the throttle body
    1. Extract the fuel in the fuel tank through the fuel tank filler hole with a pump. 2. Disconnect: Fuel hose WARNINGCover the fuel hose connections with a cloth when disconnecting them. Residual pressure in the fuel lines could cause fuel to spurt out when removing the h ...

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