FS-61 FS-70S FS-80 FS-120SE Carburettor Needle OS27481900 by O.S. Engine  [OS27481900]

Precision needle valve for O.S. Engine series

This needle valve assembly is designed as a carburettor component for the specified O.S. engine models. Its role is to allow precise low-speed fuel metering and to assist with mixture tuning during bench setup and initial running.

Compatibility is limited to the engine model codes listed in the title: FS-61, FS-70S, FS-80, FS-120SE. Confirm fitment against the engine's parts diagram or official documentation before fitting to other models.

Installation notes - general guidance:

• Prepare a clean work surface and remove fuel from the system before opening the carburettor to prevent contamination.
• Install the needle in the same orientation as the original, ensuring all seats and clips are refitted securely.
• Once fitted, make conservative adjustments and check idle and throttle progression in a safe testing area.

Tuning and maintenance tips:

• Adjust the low-speed needle in small increments to find a predictable idle and smooth throttle response.
• Regularly examine the needle tip and seat for scoring or residue and clean them with a carburettor-safe solvent as needed.
• Log your starting needle positions so you can revert if a change degrades performance.