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:

    Installing the shift shaft
    1. Install: Stopper lever "1" Stopper lever spring "2" NOTE: Install the stopper lever spring as shown in the illustration. Hook the ends of the stopper lever spring onto the stopper lever and the crankcase boss "3". Mesh the stopper lever with the shift drum segment assembly. ...

    Starting circuit cut-off system operation
    If the engine stop switch is set to " " and the main switch is set to "ON" (both switches are closed), the starter motor can only operate if at least one of the following conditions is met: The transmission is in neutral (the neutral switch is closed). The clutch lever is pulled to the ...

    Tachometer
    Tachometer Tachometer Tachometer red zone The electric tachometer allows the rider to monitor the engine speed and keep it within the ideal power range. When the key is turned to "ON", the tachometer needle will sweep once across the r/min range and then return to zero r/min ...

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