Yamaha YZF-R125 Service Manual: Installing the valves

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

1. Deburr:

  • Valve stem end (with an oil stone)

Installing the valves


2. Lubricate:

  • Valve stem "1"
  • Valve stem seal "2"
    (with the recommended lubricant)

Installing the valves


3. Install:

  • Lower spring seat "1"
  • Valve stem seal "2"

  • Valve "3"
  • Valve spring "4"
  • Upper spring seat "5" (into the cylinder head)

NOTE:

  • Make sure each valve is installed in its original place.
  • Install the valve springs with the larger pitch "a" facing up.

Installing the valves


b. Smaller pitch

4. Install:

  • Valve cotters "1"

NOTE:

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


Installing the valves


5. To secure the valve cotters onto the valve stem, lightly tap the valve tip with a soft-face hammer.

CAUTION:

Hitting the valve tip with excessive force could damage the valve.

Installing the valves


    Checking the valve springs
    The following procedure applies to all of the valve springs. 1. Measure: Valve spring free length "a" Out of specification Replace the valve spring. 2. Measure: Compressed valve ...

    Cylinder and piston
    ...

    Other materials:

    Checking the ignition spark gap
    1. Check: Ignition spark gap Out of specification Perform the ignition system troubleshooting, starting with step 5. Refer to "TROUBLESHOOTING" on page 8-3. NOTE: If the ignition spark gap is within specification, the ignition system circuit is operating normally. a. Disconnect the spa ...

    Removing the front brake caliper
    NOTE: Before disassembling the brake caliper, drain the brake fluid from the entire brake system. 1. Remove: Brake hose union bolt "1" Copper washers "2" Brake hose "3" NOTE: Put the end of the brake hose into a container and pump out the brake fluid carefully. ...

    Checking the lean angle sensor
    1. Remove: Lean angle sensor 2. Check: Lean angle sensor output voltage Out of specification Replace. a. Connect the lean angle sensor to the wire harness. b. Connect the pocket tester (DC 20 V) to the lean angle sensor coupler as shown. Positive tester probe yellow/green "1" Neg ...

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