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:

Setting the normal mode
NOTE: The engine speed, coolant temperature, and fault code, if detected, can be displayed on the LCD of the FI diagnostic tool when the tool is connected to the vehicle and is set to the normal mode. 1. Set the main switch to "OFF" and the engine stop switch to "". 2. Disconnect the self- ...

General tightening torque specifications
This chart specifies tightening torques for standard fasteners with a standard ISO thread pitch. Tightening torque specifications for special components or assemblies are provided for each chapter of this manual. To avoid warpage, tighten multi-fastener assemblies in a crisscross pattern and ...

Checking the condition of the bulb sockets
The following procedure applies to all of the bulb sockets. 1. Check: Bulb socket (for continuity) (with the pocket tester) No continuity Replace. NOTE: Check each bulb socket for continuity in the same manner as described in the bulb section, however, note the following. a. Install a ...