Huge displacement increase means huge power increase Stock crankcase, oil pump and cam cover can be reused Silver finish heads matches factory finish, giving bike a "sleeper" advantage Original crankcase is used, so original engine serial number is retained Kit features 91cc S&S Cycle heads with 10.8:1 compression ratio, S&S Cycle 4-1/8" bore cylinders and pistons, a 4-5/8" stroke flywheel assembly, chain drive S&S Cycle 640 Easy Start cams, tappets, S&S Cycle pushrods, roller rocker arms, and all required hardware, gaskets and instructions .045" MLS head gaskets used Adds .075" to engine height