2. Restore the valve seats in the cylinder head using a cutter.
3. Carefully file the seat at a 45° grinding angle, removing only as much metal as necessary to ensure a smooth, concentric seat surface.
4. Chamfer the top and bottom edges of the seat at the angles shown in the figure.
Check the valve seat band width and adjust accordingly.
5. Make another light pass at a 45° sharpening angle and remove any burrs created by the other tool.
Valve seat belt width:
| Standard (new) | 1.25-1.55 mm |
| Limit | 2.0 mm |
6. After regrinding the seat, check whether the valve fits evenly to the seat:
- Apply composition (A) containing red lead to the working surface of the valve.
- Insert the valve into its original place in the cylinder head, then lift it up and press it against the seat several times.
7. The actual contact surface (B), indicated by the red lead compound, must be located in the center of the saddle.
- If it is located too high (closer to the valve stem), it is necessary to re-process it with a sharpening angle of 67.5° and "lower" it, then go through it again with a sharpening angle of 45° and restore the width of the valve seat belt.
- If it is located too low (closer to the edge of the valve), re-processing should be carried out with a sharpening angle of 35° (from the intake side) or 30° (from the release side) and "lift" it, then go over it again with a sharpening angle of 45° and restore the width of the valve seat belt.
Note: The finishing pass should always be done at a 45° sharpening angle.
8. Insert the intake and exhaust valves into the cylinder head and measure the valve stem height (A) after installation.
Height of intake valve stem after installation: Standard (new): 40.8-41.0 mm
Height of exhaust valve stem after installation: Standard (new): 54.6-54.8 mm
9. If the valve stem height after installation exceeds the nominal value, replace the valve and recheck. If it still exceeds the nominal value, replace the cylinder head; the valve seat in the head is too deep.