This 3-31/32" stroke 8-1/2" diameter flywheel assembly replaces the original flywheels in S&S® 74" KN74 engines with generator/generator style crankcases for 1936-'47 HD® big twins. Flywheels are CNC machined from heat-treated, closed die, steel forgings, and are stronger than cast iron or late style steel flywheels. Dynamically balanced and fully assembled with premium quaility S&S® mainshafts and heavy duty 7.440" connecting rods.