S&S Cycle largest big bore kit for Sportster models that bolt to stock crankcases Can typically increase horsepower to over 90hp with proper exhaust, camshafts, CNC ported heads, while using the stock fueling system Forged pistons are dome top 11.2:1 compression ratio (based on 60cc combustion chambers) Each piston is fitted with rings and wristpins, and have larger then stock valve pockets that accept up to 2.00" valves Cylinders are 3-9/16", available in silver or wrinkle black finish and come with MLS head, base, and exhaust gaskets; Note: S&S Cycle cylinders match the 1986-2003 cylinder heads. 2004-15 have a slight difference in fin profile.; Note: Cannot run stock 883 cylinder heads with this kit