O.S. Engine OS22681320 Throttle Stop Screw for 20D 20F 2FB Carburettors  [OS22681320]

Part purpose and fit

This throttle stop screw is supplied as a direct replacement for carburettors designated 20D, 20F and 2FB used on O.S. Engine models. The part limits the closed position of the throttle valve so idle speed can be consistently reproduced and needle adjustments remain stable.

The screw seats against the throttle stop tab or cam surface in the original carburettor layout for those engines. Installation normally requires removing or loosening the old stop, fitting the new screw, and then setting the idle with progressive adjustments while the engine is running.

When tuning, adjust in small steps and verify that the throttle linkage clears all mechanical stops through the full travel. Clean any fuel deposits from the area and check the threads to ensure dependable repeated settings.