Ding Ding, It's an 820, the SA is the designation of whom the engines were built for. The karting version of the West Bend 820 were rated at 10 HP @8000 rpm. The Industrial engines ( Gorman Rupp, Rokan, Utility etc) were rated 6 HP to 7 HP, depending on head gasket thickness, timing, carburetor size and rpm. The only 820's that came with a single ring piston were the Copperhead and Vintage 820 which were designed by Dave Bonbright for US Motor around 2007, those came with a single ring piston, two tool steel rings in one ring grove, a manifold that used a Boysen reed, a Tilloston HR 191 carb, a Horstman style head, boost ported, squared exhaust, siamesed intake ports, electronic ignition etc, these were not HP rated but probably put out 15 to 18 HP on gas, 20 to 24 on alcohol. The Copperhead and Vintage 820 are no longer offered from US Motor. I have a West Bend (Chrysler) 610 (100cc), 300 were built to compete against the Mac 91 in the stock karting classes back in the late 60's, The model is SA616, serial 4514. They were built by Chrysler for Dave Liberton, he was going to submit them to the International Karting Federation (IKF) to my understanding he never did submit the project. This engine came with a thin ring piston (two rings, .030 thick) an intake manifold that took the McCulloch 91 reed cage, a large Tillotson HR carburetor, boost ported. I put a GEM V12 intake with two HL293 alky carbs, Horstman head, shaved flywheel, Horstman muffler, it runs very good for a vintage kart setup. The SA may stand for Special Application.