Yamaha YZF-R125 Service Manual: Removing the valves

The following procedure applies to all of the valves and related components.

NOTE:

Before removing the internal parts of the cylinder head (e.g., valves, valve springs, valve seats), make sure the valves properly seal.

1. Check:

  • Valve sealing Leakage at the valve seat Check
    the valve face, valve seat, and valve seat width.

    Refer to "CHECKING THE VALVE SEATS" on page 5-20.

a. Pour a clean solvent "a" into the intake and exhaust ports.

b. Check that the valves properly seal.

NOTE:

There should be no leakage at the valve seat "1".

Removing the valves


2. Remove:

  • Valve cotters "1"

NOTE:

Remove the valve cotters by compressing the valve spring with the valve spring compressor and the valve spring compressor attachment "2".


Removing the valves


3. Remove:

  • Upper spring seat "1"
  • Valve spring "2"
  • Valve "3"
  • Valve stem seal "4"
  • Lower spring seat "5"

NOTE:

Identify the position of each part very carefully so that it can be reinstalled in its original place.

Removing the valves


    Valves and valve springs
    ...

    Checking the valves and valve guides
    The following procedure applies to all of the valves and valve guides. 1. Measure: Valve-stem-to-valve-guide clearance Out of specification Replace the valve guide. Valve-stem-to-valve ...

    Other materials:

    Checking the shift forks
    The following procedure applies to all of the shift forks. 1. Check: Shift fork cam follower "1" Shift fork pawl "2" Bends/damage/scoring/wear Replace the shift fork. 2. Check: Shift fork guide bar Roll the shift fork guide bar on a flat surface. Bends  Replace. ...

    Replacing a turn signal light bulb
    Remove the turn signal light lens by removing the screw. Screw Remove the burnt-out bulb by pushing it in and turning it counterclockwise. Insert a new bulb into the socket, push it in, and then turn it clockwise until it stops. Install the lens by installing ...

    Checking the ignition timing
    NOTE: Prior to checking the ignition timing, check the wiring connections of the entire ignition system. Make sure all connections are tight and free of corrosion. 1. Remove: Rider seat Left lower side cowling Refer to "GENERAL CHASSIS" on page 4-1. 2. Remove: Timing mark acces ...

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