91SR Carburetor Throttle Barrel YSS9121 by YS Engine  [YSS9121]

Throttle barrel — 91SR fit and function

The YS Engine YSS9121 throttle barrel is supplied as a replacement slide for 91SR model engines and sits within the carburettor to regulate airflow and throttle response. It is the principal moving element controlling midrange and transient behaviour.

Use is intended for 91SR engines only. Prior to installation, check that the new barrel matches the existing part in diameter, length and any locating features to ensure correct movement and clearance inside your carburettor.

Fitting procedure: detach the carburettor, examine mating surfaces, and carefully transfer the throttle slide while keeping orientation. Refit and test that the linkage operates smoothly through the full travel. Small adjustments to linkage geometry or idle may be necessary to restore correct running.

Tuning note: replacing a worn barrel can re-establish steady idle and more consistent throttle transitions, making subsequent carburettor fine-tuning more predictable. Keep the barrel and bore clean and inspect for wear as part of routine servicing.