A special tool is required to lap the valves.
In addition, you will need lapping paste and kerosene to lap the valves.
1. Remove the cylinder head (see «Replacing the cylinder head gasket»).
2. Remove the valves from the cylinder head and thoroughly clean the valves and seats (see «Dismantling, repair and assembly of the cylinder head»).
3. Insert the valve into the cylinder head.
4. Apply a thin layer of lapping paste to the valve face.
5. Attach the valve stem to the valve lapping tool and turn the valve in both directions with the tool, periodically pressing the valve against the seat.
6. An external sign of satisfactory grinding is a solid matte gray color of the valve face and seat.
7. After lapping, thoroughly wipe the valve and seat with a clean cloth and rinse to remove any remaining lapping paste. Check the tightness of the valve, for which install it in the head of the block with springs and crackers. Then lay the cylinder head on its side and pour kerosene into the channel that is closed by the valve. If kerosene does not seep into the combustion chamber within 3 minutes, the valve is tight.