O.S. Engine OS21781970 10LA and 15LA Carb Needles  [OS21781970]

10LA/15LA needle replacement guide

The O.S. Engine OS21781970 twin needles fit the 10LA and 15LA needle seats used on many small glow-model carburettors and are sold as direct replacement parts for regular engine maintenance. They aim to replicate the factory adjustment feel and provide repeatable seating for accurate tuning sessions.

Operationally the needle regulates fuel entry at the needle valve, which changes idle characteristics and mixture strength. Replacing worn needles can eliminate unstable idle, hesitation, or the need for large compensation during tuning. Note that this listing is for the needle components only, not a full carburettor assembly.

Installation tips: only use these needles in carburettors designed for 10LA or 15LA profiles, check for smooth movement and proper seating, then adjust mixture and idle according to your engine's established method. Make minute changes when tuning and validate settings after an initial run to ensure consistent engine response.