This 4-5/8" stroke 8-1/2" diameter flywheel assembly replaces the original flywheels in S&S® T143 engines for 1999-'06 HD® big twins. Sprocket shaft does not have a stock style bearing race pressed on. This flywheel assembly is for crankcases with Timken® sprocket shaft bearing. Pinion shaft has sprocket to drive balancer chain.