91/120/140 Engine Regulator Screws YSF1251 - YS Engine  [YSF1251]

Overview of the regulator screw kit

This regulator screw set is offered as an RC-scale replacement pack for 91, 120 and 140 engine sizes, meant for direct replacement when factory screws are worn or need renewing. The set suits model engine carburetor and regulator mounting points.

Compatibility is restricted to the 91, 120 and 140 size labels in the product name, so confirm your engine uses one of those sizes before fitting. The information here is limited to RC engine fitment and setup guidance.

Fitting advice: use the correct hex driver, start screws by hand to prevent cross-threading, tighten to a firm seat without over-torque, recheck linkage geometry after installation and run the engine gently to confirm idle stability and throttle response.

Tuning impact: refitted regulator screws can restore fixed adjustment stops and remove slop in linkages, improving repeatability of needle and regulator settings for more consistent tuning results.