S&S 131 Big Bore Stroker Cylinder & Piston Kits For Harley Milwaukee-Eight S&S Cycle has been making big bore kits as early as the 60s and has it down to a science at this point. They have used their latest efforts to allow your M8 open a whole new level of performance of these engines. Combining a new design forged piston with their 4.25 cylinders to net a tire melting 131 cubic inches when paired with their 4.625 stroker crank. Features Power increase due to increased displacement Works with stock crankcases Original engine serial numbers are retained .045 MLS (multi-layered steel) head gaskets Retains stock engine height Includes 131 Cam Cover Badge