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".

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".

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.