504160 Lock plate, sprocket & pinion shaft

This small lock plate secures the sprocket and pinion shaft assembly, preventing loosening under the constant torque loads generated by the primary drive. Designed for 1936 to early 1981 Big Twin and 1952 to early 1981 XL Sportster models, it serves as a critical safety component in the engine's bottom end. The lock plate tabs bend over the retaining nut once torqued to specification, providing a positive mechanical lock that vibration alone cannot defeat. Always replace this lock plate with a new one during any service that requires sprocket or pinion shaft removal, as reusing a previously bent plate compromises its locking effectiveness.