Yamaha YZF-R125 Service Manual: Checking the valves and valve guides

Yamaha YZF-R125 Service Manual / Engine / 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-guide clearance = Valve guide inside diameter "a" - Valve stem diameter "b"

Checking the valves and valve guides

2. Replace:

Valve guide

NOTE:

To ease valve guide removal and installation, and to maintain the correct fit, heat the cylinder head to 100 C (212 F) in an oven.

a. Remove the valve guide with the valve guide remover "1".

Checking the valves and valve guides

b. Install the new valve guide with the valve guide installer "2" and valve guide remover "1".

Checking the valves and valve guides

a. Valve guide position

c. After installing the valve guide, bore the valve guide with the valve guide reamer "3" to obtain the proper valve-stem-to-valve-guide clearance.

Checking the valves and valve guides

NOTE:

After replacing the valve guide, reface the valve seat.

3. Eliminate:

Carbon deposits (from the valve face and valve seat)

4. Check:

Valve face Pitting/wear Grind the valve
face.
Valve stem end Mushroom shape or diameter larger than the body of the valve stem Replace
the valve.

5. Measure:

Valve margin thickness D "a" Out of specification Replace
the valve.

Checking the valves and valve guides

6. Measure:

Valve stem runout Out of specification Replace
the valve.

NOTE:

When installing a new valve, always replace the valve guide.
If the valve is removed or replaced, always replace the valve stem seal.

Checking the valves and valve guides

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 th ...

Checking the valve seats

The following procedure applies to all of the valves and valve seats. 1. Eliminate: Carbon deposits (from the valve face and valve seat) 2. Check: Valve seat Pitting/wear Replace the ...

Other materials:

Operation and important riding points
Read the Owner's Manual carefully to become familiar with all controls. If there is a control or function you do not understand, ask your Yamaha dealer. WARNING Failure to familiarize yourself with the controls can lead to loss of control, which could cause an accident or injury. TIP ...

Removing the swingarm
1. Stand the vehicle on a level surface. WARNINGSecurely support the vehicle so that there is no danger of it falling over. NOTE: Place the vehicle on a suitable stand so that the rear wheel is elevated. 2. Measure: Swingarm side play Swingarm vertical movement a. Me ...

Intake air temperature sensor
1. Check: Intake air temperature sensor resistance Out of specification Replace the throttle body. a. Connect the pocket tester ( × 1k) to the throttle body sensor assembly coupler as shown. Positive tester probe brown/white "1" Negative tester probe gray/black ...