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

Adjustable mixture screw for nitro carburettors

This mixture control screw is an RC carburettor spare intended for the O.S. Engine models listed. It is the main user-adjustable part for setting the fuel/air ratio and improving idle stability and throttle response on nitro model engines.

Use is confined to the models named in the product title: 2B, 2C, 21FSR, and 25FSR. The part is supplied as a direct replacement and should be fitted only to compatible engine types.

To install, access the carburettor mixture port and replace the existing screw, maintaining the same seating angle and engagement. Adjust in small increments and monitor idle and throttle response; overly rich settings will reduce idle speed and produce darker exhaust, while lean settings increase idle and engine heat.

For tuning best practice, run the engine to normal temperature, then make small, measured turns and verify smooth acceleration and steady idle. If the engine runs rough after an adjustment, revert to the previous setting and check mounting and fuel/air lines for issues.