The piston K 43556 is an important pressure-responsive and moving component of the automatic starting-air stop valve used in the starting-air system of the Adriadiesel/Jugoturbina/Zgoda/Sulzer ZV40/48 engine. Its primary function is to support the pneumatic actuation of the valve by converting compressed-air pressure into controlled mechanical movement, enabling the starting-air stop valve to respond accurately to the operating conditions and control sequence of the engine starting system. Working together with the associated piston ring K 43570, guiding surfaces, and other internal valve components, the piston helps maintain the required pressure separation and ensures smooth, repeatable movement during valve operation. Accurate piston dimensions, surface finish, alignment, and suitable operating clearances are particularly important because excessive wear, contamination, deformation, or damaged sealing elements can result in internal air leakage, sticking, delayed response, or incomplete valve movement. During service, the K 43556 piston is exposed to repeated pressure cycles, axial movement, friction, vibration, and extended periods of standby readiness, requiring good dimensional stability and resistance to wear and corrosion. During maintenance or overhaul, the piston should be inspected for scoring, uneven wear, corrosion, deposits, dimensional deviations, and damage to the piston-ring groove, while the condition of the associated K 43570 piston ring and mating surfaces should also be verified. By providing dependable pressure-actuated movement and supporting effective internal sealing, the K 43556 piston contributes to reliable automatic starting-air control, reduced compressed-air losses, consistent valve response, and long-term operational readiness of the ZV40/48 engine.