This is the O.S. .91HZ F3C Competition Helicopter Engine. FEATURES: Designed specifically for F3C aerobatic competition Rectangular heat sink allows engine to be enclosed entirely inside cooling shroud 61-E carburetor with thermal insulator to block heat and a needle valve control lever to control mixture from transmitter, carburetor has three adjustment controls that enable independent adjustment at idling, hovering and high speed Five holes in the top of the piston route gases to the piston ring from within to form a tighter seal with minimum blow by Ball bearing supported crankshaft Heat sink type backplate Two year limited warranty through Hobby Services beginning at date of purchase INCLUDES: O.S. .91 HZ F3C Competition Helicopter Engine with #8 glow plug, needle control lever, extra 0.2mm head gasket, cap screws and instruction manual REQUIRES: Fuel: 10%-30% nitromethane with at least 18% lubricant. Lubricants may be either castor or synthetic oil or castor/synthetic blend. Field Equipment: glow starter, fuel bulb, fuel can filter, fuel pump hexagonal starting shaft (depending on brand of helicopter) electric starter, battery and fuel tubing Muffler-Depending on heli SPECS: Displacement: 0.91 cu in (14.95 cc) Bore: 1.09" (27.7mm) Stroke: 0.98" (24.8mm) Output: 3.4 PS, 3.35 HP @ 15,000 RPM Practical RPM Range: 2000-16,000 Weight Without Muffler: 1.36lb (618g) Crankshaft Size: 5/16-24 Height from crankcase bottom to top of cylinder head: 3.9" (99mm) Height/bottom of mounting tab to top of cylinder head: 3.2" (81.2mm) Distance between mounting holes same side: 0.98" (25mm) Distance between mounting holes opposite side: 2.04" (52mm) Distance between muffler screw holes: 1.6" (42mm) Distance/bottom of mounting tab to muffler screw holes: 1.7" (42.8mm) Length from front bearing to backplate: 3.3" (84mm) Length from backplate to end of crankshaft: 4.9" (125.6mm) Width of crankcase below mounting tabs: 1.7" (43mm) Width between mounting tabs: 2.4" (61mm) Carburetor Needle Settings: High Speed: 2 turns out from fully closed Mid Range: 2 turns open Mixture Control (low speed): indentation on screw head straight up and down (vertical) jxs 10/14/10 ir/jxs