Stock 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 retaining stock appearance of the engine. Minor crankcase and cylinder modifications are required, that can easily be done with hand tools. This kit requires special pistons which must be ordered separately depending on the oversize required for the stock cylinders. Pistons are available for stock or S&S Performance Replacement cylinder heads or for S&S Super Stock cylinder heads.