Carburettor Mixture Control Screw for O.S. Engine OS22481619 (2B 2C 21FSR 25FSR)  [OS22481619]

Fine-tune mixture screw for O.S. Engine models

This mixture control screw is an exact carburettor replacement intended for the O.S. Engine units listed above. It allows precise control of the fuel/air mixture and is used to stabilise idle and improve throttle response on nitro-powered scale engines.

Compatibility is restricted to the models specified in the title: 2B, 2C, 21FSR, and 25FSR. The component is offered as a direct substitute for the original carburettor screw and must be used on the compatible engine types only.

Fitting requires removing the existing screw and installing the replacement with identical seating and engagement. Adjustments should be small and followed by checks of idle smoothness and throttle transition; rich mixtures lower idle and darken the exhaust, whereas lean mixtures raise idle and can raise operating temperature.

For best results, tune after the engine reaches normal running temperature and refine the mixture with tiny turns while confirming steady acceleration and idle. If the engine begins to run unevenly after tuning, return to the previous setting and inspect air and fuel supply components for faults.