7/ The 110ci engine in the S models is the largest ever offered in a stock Softail. From humble beginnings with an 80ci Evolution engine through to the standard 103ci engine in the rest of the line, the Softail has grown with the S models (Softail Slim S, $18,499, and Fat Boy S, $19,699) to pack 1,802cc from a 4-inch bore and a 4.374-inch stroke, giving 109 pound-feet of torque at 3,500 rpm. The regular 103 has a measly 3.87-inch bore and offers up 100 pound-feet at 3,000 rpm. The big engines in the Softail Slim S and the Fat Boy S have hydraulic clutches. That makes it easier to squeeze the stronger clutches. Because torque.