YS Series YS 91SR Heli Type 2-Stroke, Helicopter Displacement .91 cu in (14.89cc) Bore 1.6" (27mm) Stroke 1.0" (26mm) RPM Range 2,000-17,000 Output (HP/rpm) - Weight (engine only) 19.5 oz. (553g) Crankshaft Thread - Propeller Range - Included

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