O.S. Engine OS29123100 Replacement Cylinder Liner Compatible with 120AX  [OS29123100]

Fitment and Service Notes for 120AX

The OS29123100 cylinder liner is a replacement sleeve designed for the 120AX series of RC model engines. It serves as the internal wear surface and is sold as a single replacement component for engine rebuilds and routine servicing.

To install, remove the head and piston assembly, extract the old liner, inspect the cylinder seat and mating surfaces for damage, then fit the replacement liner following accepted engine service procedures. Cleaning and checking the piston and ring face prior to reassembly will help ensure reliable compression and sealing.

Using a replacement sleeve restores the engine's internal geometry which influences compression and combustion characteristics; fitting a new liner is a common maintenance step when preparing an engine for further setup or when wear impairs performance.

As a direct replacement for the 120AX family, this liner is intended for model engine maintenance and rebuilds; replace it when wear or scoring affects compression to return the engine to a serviceable state.