The disc K 43178 is a precision functional component designed for the rotary slide valve K 43173 within the starting device of the Adriadiesel/Jugoturbina/Zgoda/Sulzer ZV40/48 engine. Working as an integral part of the rotary valve arrangement, the disc helps establish the required control relationship between the valve's moving and stationary elements, supporting accurate distribution of the starting medium during the engine starting sequence. Its geometry, angular relationship, flatness, surface finish, and dimensional accuracy are important for maintaining controlled movement and the intended communication between the relevant passages as the rotary slide valve changes position. Repeated operation exposes the K 43178 to mechanical contact, friction, pressure differences, vibration, and possible contamination, making good surface condition and resistance to wear essential for dependable service. During maintenance or overhaul, the disc and its mating surfaces should be inspected for scoring, uneven wear, corrosion, deposits, deformation, or other damage that could affect movement, sealing, or distribution accuracy. By supporting the precise function of the K 43173 rotary slide valve, the K 43178 disc contributes to consistent starting-medium control, reliable starting-system operation, reduced leakage and wear, and dependable long-term starting performance of the ZV40/48 engine.