This is one of the O.S. Surpass series of 4-stroke model engines. The Surpass series is the 2nd series of 4-stroke engines (The 1st series was the FS series, discontinued and replaced by the Surpass series around 1986-7). "Surpass" refers to the fact that this series gained 30% more power than the previous FS series. FEATURES: 30% larger Intake Valves than the FS series Ringed Piston Rear-mounted updraft Carburetor Helix Gear-Driven Camshaft Ball Bearing-Supported Camshaft and Crankshaft Covered under 2-YEAR WARRANTY INCLUDES: One Assembled FS-120 Surpass w/Carb and No Pump One #F Glow Plug One Exhaust Header One Exhaust Muffler One Choke Valve Extension One Set of Instructions, Poster, and Decals (Wrenches, Choke Valve Extension, and Mounting Template Are No Longer Included per O.S.) REQUIRES: Fuel: 5%-15% nitromethane with 18% lubricant. Synthetic, castor, or a synthetic/castor blend may be used. NOTE: Certain four-cycle fuels cannot be used due to low oil content. However, SOME four-cycle fuels such as the Wildcat 4-Cycle 15% (CATP9109) may be used because it has 18% oil content. When choosing fuels for this engine, the modeler must be sure to select a fuel with at least an 18% lubricant content. Starting and Field Equipment Propeller (see SPECS) SPECS: Bore: 31mm (1.22") Stroke: 27.5mm (1.08") Power Output: 1.9 PS, 1.87HP at 11,000 RPM Weight-Without Muffler: 30.5oz (864g) Weight-With Muffler: 33.3oz (944g) Practical RPM Range: 2,000 - 11,000 RPM Crankshaft Thread Size: 5/16-24 Valve Clearance: Between .04mm and .1mm (or between .0015" and .004", measured between the valve tip and rocker arm) Length: 104mm (4.09") from backplate to the front of drive washer Width: 47mm (1.85") width of engine neglecting the mounting flanges 58mm (2.28") distance between the mounting hole centers Height: 138.5mm (5.45") Suggested Prop(s): 13x11, 13x12, 14x10, 14x11, 15x8, 16x6, 16x7, 17x6 Construction: Aluminum and Aluminum alloys Needle Settings: High Speed: 2.5 - 3 turns out from fully closed Low Speed: Edge of larger sleeve centered, looking down the neck of the carb COMMENTS: Some differences between 4-Stroke and 2-Stroke engines. 4-strokes are quieter. 4-strokes get better fuel economy. 2-strokes generate more RPM (11,000-13,000 RPM with prop while 4-strokes rev to around 9,500 RPM) 4-strokes generate much more torque and will swing a larger prop. 4-strokes have a realistic sound, like a real aircraft engine. JBN 7/20/93 ir/jl updt lmm 3/31/09