The piston ring K 27409 is a small but vital sealing component that fits piston K 27404 in the starting-valve mechanism of the ZV40/48. Its job is to maintain a reliable seal under varying pressure and temperature, preventing blow-by and ensuring the piston transmits force efficiently. Manufactured to tight tolerances from resilient, oil- and heat-resistant material, the ring contributes directly to consistent valve actuation and longevity — regular checks for wear, cracking or loss of spring tension help prevent leaks and erratic starting behavior.