O.S. Engine OS29088300 Mixture Control Valve Assembly for 61E-R and 91HZ-R  [OS29088300]

Mixture Control Valve Assembly

This mixture control valve assembly is a direct replacement component designed for use with O.S. Engine models 61E-R and 91HZ-R, specified for RC-scale model engine carburettors. It serves the role of fine-tuning the fuel/air ratio at low and idle throttle settings to help stabilise idle and improve throttle transition during tuning sessions.

As an RC accessory, the assembly integrates with the carburettor mounting and linkage common to the named O.S. models, allowing technicians to adjust mixture without replacing the entire carburettor. Installation is typically done during routine engine maintenance or when restoring consistent idle behaviour after changes to needle settings or intake components.

Tuning guidance: make incremental adjustments and re-check engine response under controlled running conditions, focusing on idle quality and throttle roll-on. Verify linkage free-play and that threads and seals seat correctly; a secure fit and clean mating surfaces reduce the chance of air leaks that can mask mixture settings.

Because this is an RC-scale replacement part, ensure compatibility by matching the part designation to your engine model before installation, and perform test runs on a stand or short tethered runs where applicable to confirm the desired mixture outcome.