O.S. Engine OS27481900 Needle Valve Assembly for FS-61 FS-70S FS-80 FS-120SE  [OS27481900]

Needle valve assembly for O.S. engines

This needle valve assembly is an RC-scale carburettor part intended for use with the listed O.S. engine models. It serves the tuning role inside the carburettor, providing the operator a mechanical interface to adjust low-speed fuel metering and assist in mixture setup during bench tuning and run-in.

Compatibility is limited to the engine model codes stated in the product name: FS-61, FS-70S, FS-80, FS-120SE. Do not assume fitment to other engines without confirming with the engine's parts diagram or manufacturer documentation.

Installation notes — general guidance:

• Work on a clean bench and remove fuel before servicing the carburettor to avoid contamination.
• Replace the needle assembly using the engine's stock carburettor orientation, securing any retaining clips or seatings as originally fitted.
• After installation, perform conservative needle adjustments and verify idle and throttle response in a safe test environment.

Tuning and maintenance tips:

• Use small incremental turns when adjusting the low-speed needle to find a stable idle and smooth throttle transition.
• Inspect the needle tip and seat for wear or residue regularly, and clean with appropriate carburettor-safe solvent if needed.
• Document baseline needle settings before each change so you can return to a known starting point during testing.