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 this series gaining 30% more power than the previous FS series. FEATURES: Specially developed PD-07 pump New 70N carb Ball bearing-supported camshaft and crankshaft New F-5020 Silencer Two year warranty INCLUDES: One Assembled Engine w/Carburetor and #F Glow Plug One Muffler w/Manifold One Set of Instructions, O.S. Poster, and Decal (Mounting Template Is No Longer Included per O.S.) One additional coarse needle for less sensitive carb adjustment. 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 a 18% lubricant content. Starting and Field Equipment. Propeller (see SPECS) SPECS: Bore: 30.4mm (1.20") Stroke: 27.5mm (1.08") Power Output: 2.1 PS, 2.07 HP at 12,000 RPM Practical RPM Range: 2,000 - 12,000 RPM Weight-Without Muffler: 32.5oz (921g) Weight-With Muffler: 35.3oz (1000g) 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: 102mm (4.09") from backplate to the front of the drive washer Width: 47mm (1.85") width of engine neglecting the mounting flanges 58mm (2.28") distance between the mounting hole centers Height: 139.5mm (5.49") Suggested Prop(s): 14x9, 14x10, 14x11, 15x8, 15x9, 15x10, 16x6, Construction: Aluminum and Aluminum alloys Needle Settings: High Speed: 1.5 turns out from fully closed Low Speed: 2.5 turns out from fully closed with the throttle fully closed COMMENTS: Some differences between 2-Stroke and 4-Stroke engines: 4-Strokes are quieter. 4-Strokes get better Fuel Economy 2-Strokes generate More RPM (11,000-13,000 RPM with prop and 4-Strokes rev to around 9,500 RPM) 4-Strokes generate much more torque and will swing a larger prop. 4-Strokes have a more realistic sound, like a real aircraft engine. The new Surpass engines (Version II and III) have more power than their predecessors and they also have more corrosion prevention on the inside of the crankcases. 5-7-97 djg ir/jl updt lmm 3/31/09