O.S. Engine OS23181200 Carburettor Rotor - 21K 35AX Performance Part  [OS23181200]

Tuning and throttle control component

This carburettor rotor is supplied under the O.S. Engine range and carries the model number OS23181200. It is intended for use in compatible O.S. Engine carburettor assemblies, where it governs airflow metering and influences mixture response as part of the carburettor's control system.

From a tuning perspective the rotor has a direct effect on throttle progression and needle behaviour, so builders replace it to recover a linear throttle feel or to remove erratic idle and mid-range issues caused by wear. The focus here is on fitment, handling, and practical tuning use rather than presenting unverifiable specs.

Fitting tips: inspect the carburettor shaft and bore for wear before installation, carefully align the rotor to the shaft spline, and avoid forcing the part into place. Once fitted, perform idle and throttle checks on a bench stand and make small mixture tweaks to find the new baseline.

Care and inspection: watch for scoring patterns on the rotor face and where it meets the shaft, ensure the rotor rotates freely without binding, and replace if significant play exists. Keep fasteners and small parts separated during service and use the right tools to prevent housing damage.