YS Engine YSF1251 Regulator Screw Set 91 120 140  [YSF1251]

Regulator screw set overview

This regulator screw set is an RC-scale replacement kit labelled for 91, 120 and 140 engine sizes, intended as direct swap hardware where original regulator screws are worn or need refresh. The pack is aimed at model-scale engines and their carburetor or regulator attachments.

Compatibility is limited to the 91, 120 and 140 size designations shown in the product name, so confirm your engine references those numbers before fitting. This article keeps to practical fitment and tuning advice without implying any non-RC use.

Installation tips: use the correctly sized hex driver, thread screws carefully to avoid cross-threading, tighten to a snug fit and avoid over-torquing, check linkage alignment after installation and run the engine at low throttle to verify stable idle and response.

Tuning role: replacing regulator screws can restore repeatable adjustment points and reduce play in linkage or carburetor linkages, helping consistent needle or regulator settings during setup and field servicing.