25XZ-Series Inner Head Replacement - OS22854100 for O.S. Engine  [OS22854100]

This inner head is a direct replacement component identified as OS22854100 for use with O.S. Engine 25XZ family engines. It is designed as an internal head piece to serve as a spare for restoring worn or damaged upper-end parts on RC nitro engines.

Use this inner head when inspection reveals wear, cracks, or sealing faults in the head assembly of a 25XZ-series unit. Swapping the inner head can correct sealing problems and return the engine to service without needing a full engine replacement.

For installation, follow the engine service manual: disassemble the head, check gaskets and O-rings, replace any damaged seals, and reassemble using correct fastener torque and engagement. Verify sealing and perform run-in routines in line with the engine manufacturer's guidance before normal operation.

Viewed as a consumable spare, the inner head supports bench repairs, head swaps during rebuilds, and scheduled servicing to maintain consistent engine condition across repair cycles.