S&S 89" Stock Bore Stroker Kit For 1984-'99 Carbureted Big TwinsStock 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