A-B1262539-AI SPRING-THR RETURNOne New Aftermarket Replacement Throttle Return Spring Fits Briggs and Stratton (B&S) Engines This aftermarket replacement throttle return spring (Spring Thr Return) Fits Briggs and Stratton small engines used in lawn mowers, riding tractors, and other outdoor power equipment. The throttle return spring ensures the throttle plate returns to its idle position when the operator releases the throttle control, maintaining proper engine speed regulation