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

Regulator screw set essentials

This regulator screw set functions as an RC-scale spare kit specified for 91, 120 and 140 engine sizes and is intended as a direct replacement when original regulator screws are worn or require renewal. The kit applies to model engine carburetor and regulator mounting interfaces.

Compatibility note: the set is limited to the 91, 120 and 140 size numbers listed in the product title, so confirm your engine uses one of those sizes before fitting. The write up confines itself to RC engine fitment and setup.

Fitting hints: use the correct hex driver, align screws carefully to avoid cross-threading, tighten until snug without over-torquing, verify linkage alignment after installation and run the engine at low throttle to ensure steady idle and consistent response.

Adjustment role: fitting fresh regulator screws helps re-establish fixed adjustment points and reduces play in linkages, aiding repeatable needle and regulator tuning during maintenance and trackside servicing.