Carburetor Rotor Upgrade for 40L-R and 55HZ-R - OS25881210 by O.S. Engine  [OS25881210]

How this rotor affects tuning for 40L-R and 55HZ-R

This replacement rotor fits O.S. Engine carburettors stamped 40L-R and 55HZ-R and provides the controlled rotation used to operate the throttle slide. Proper rotor condition supports stable mixture and idle characteristics on small glow engines used in model vehicles and aircraft.

Fit and role: The rotor matches the required seating for the 40L-R and 55HZ-R and operates as the rotating element that engages the slide and linkage. It is supplied for maintenance tasks where worn internals are replaced to restore consistent throttle behaviour.

Installation notes: Sold as the individual rotor part for use during carburettor disassembly and reassembly. Observe the manufacturer’s assembly order, check that the rotor and slide move freely after reassembly, and confirm idle and mixture settings on the bench before running the engine.

Tuning and service guidance: While the rotor does not directly change jetting, replacing a degraded rotor can eliminate erratic throttle response that disrupts tuning. After installation verify smooth slide travel, then re-establish needle settings and linkage geometry as part of tune-up checks.