S&S Cycle SS32-2230 4 5/8" 89ci Stroker Flywheel Assembly for Harley-Davidson Evolution Big Twin 84-99Stock bore stroker kits have always been an economical way to increase the displacement of your engine. This S&S 89" stock bore stroker kit upgrades carbureted 80" HD 80 Evolution big twin engines to 89" displacement at approximately 9. 25: 1 compression. Includes a dynamically balanced 4 5 8" stroke flywheel assembly complete with S&S heavy duty connecting rods and mainshafts. Stock bore stroker kits reuse the stock cylinders, saving cost and