What is the function of a lapping stick in valve maintenance?

The function of a lapping stick in valve maintenance is to spin the valves during the reconditioning process. This is a critical step in ensuring a proper seal between the valve and the valve seat. When lapping the valves, a fine abrasive compound is applied, and the lapping stick is used to rotate the valve against the seat. This action helps to smooth out any imperfections, ensuring that the surfaces are well-mated and providing a tight seal, which is essential for optimal engine performance. The process helps to prevent air and fuel leaks, which can lead to inefficient combustion and decreased engine efficiency. Proper use of the lapping stick can significantly extend the life of engine components.