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 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 from the piston ring grooves and piston rings. 2. Install: Piston ring (into the cylind ...

    Troubleshooting charts
    Starting problems or poor engine performance Starting problems or poor engine performance Engine overheating WARNING Do not remove the radiator cap when the engine and radiator are hot. Scalding hot fluid and steam may be blown out under pressure, which could cause serious injury. Be ...

    Removing the crankshaft
    1. Remove: Crankshaft "1" NOTE: Remove the crankshaft with the crankcase separating tool "2". Make sure the crankcase separating tool is centered over the crankshaft. CAUTION: To protect the end of the crankshaft, place an appropriate sized socket between the c ...

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