Piston Ring Replacement for 50SX-H, 46FX-H, 46SF - OS25303400 by O.S. Engine  [OS25303400]

Specified piston ring for the listed engine variants

This piston ring serves as a direct replacement for the O.S. engine models referenced in the product name. It is a service part meant for routine maintenance or full rebuild procedures.

To install, disassemble the engine to remove the head and sleeve so the piston is accessible. Extract the worn ring and fit the replacement carefully, making sure not to damage the piston, ring groove, or cylinder surface. Use suitable tools and a clean workspace to reduce the risk of nicking components.

While a new ring does not alter bore or piston geometry, it reinstates sealing performance, which in turn stabilizes compression and combustion for consistent tuning. Always measure the ring end-gap and carry out a measured run-in before committing to final jetting or timing adjustments.

Confirm compatibility with the model codes listed in the product title prior to purchase: 50SX-H, 46FX-H, or 46SF.