Our Janssen Motorsports 513 big bore stroker kit was developed to provide the big horsepower seeker with a reliable alternative. The 513 kit provides significant torque enhancements over a stock bore YFZ. The kit comes with everything you need including our big bore plated cylinder, big bore coated piston and rings, adjustable timing gear, top end gasket kit and our stroker crank assembly fitted with our Outlaw knife edge connecting rod.