Features :
- O.S 18650 .91HZ Ring 61E
- 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

Specifications :
- Displacement: 0.91 cu in (14.95 cc)
- Bore: 1.09" (27.7mm)
- Stroke: 0.98" (24.8mm)
- Output: 3.4 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)

Contents :
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