Replacement Carburetor Rotor OS25881210 for O.S. Engine 40L-R & 55HZ-R  [OS25881210]

Rotor construction and purpose for 40L-R / 55HZ-R

This rotor is a service component produced for O.S. Engine carburettors carrying the 40L-R and 55HZ-R designations. It provides the rotational movement inside the carburettor that controls throttle action and assists with mixture and idle behaviour on small glow engines used in models.

Fit and role: Manufactured to match the rotor seating profiles of the 40L-R and 55HZ-R, the part serves as the rotating interface with the carburettor slide and linkage. It is intended for maintenance and repair when replacing worn internal parts to recover consistent throttle feel.

Installation notes: Supplied as the single rotor component for installation during carburettor strip down and rebuild. Adhere to the carburettor maker’s specified assembly sequence, confirm correct alignment and unobstructed movement, and verify idle and mixture on the bench before returning the model to use.

Tuning and service guidance: While the rotor does not change jetting by itself, a worn rotor can cause inconsistent throttle feel that affects mixture stability. Replacing it can remove binding; afterward check slide travel and fine tune needle and linkage geometry as part of routine setup.