O.S. Engines .91HZ-R 3C Speed Red 61G OSM18647
OSM18647 O.S. Engines .91HZ-R 3C Speed Red 61G

O.S. Engines .91HZ-R 3C Speed Red 61G OSM18647

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O.S. Engines 91 HZ-R 3C speed helicopter engine is designed for all-out F3C competition. Demand Regulator System ensures consistent fuel delivery from full to empty. 170ยบ exhaust timing for optimal horsepower and stable hovering. Newly designed combustion chamber shaped to match the big bore carburetor and advanced exhaust cylinder timing. 0.456" (11.6mm) Big Bore carburetor for greatest power needed for F3C maneuvers. Crankshaft counter-weight reduces vibration at high RPM.
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

Displacement: 0.91cu in (14.9cc)
Bore: 1.09" (27.7mm)
Stroke: 0.98" (24.8mm)
Output: 3.6 PS, 3.55 HP @ 15500 RPM
Practical RPM Range: 2,000-16,500
Weight (w/o Muffler): 21.2oz (603g)
Crankshaft Size: 5/16-24
Height from crankcase bottom to top of cylinder head: 4" (103mm)
Height/bottom of mounting tab to top of cylinder head: 3.1" (79mm)
Distance between mounting hole centers same side: 0.98" (25mm)
Distance/mounting hole centers opposite side: 2" (52mm)
Distance/center of muffler screw holes: 1.6" (42mm)
Distance/bottom of mounting tab to muffler screw holes: 1.7" (42.8mm)
Distance/crankshaft center to throttle control arm: 1.6" (42mm)
Length from front bearing to backplate: 3.3" (84mm)
Length from backplate to end of crankshaft: 4.5" (116mm)
Width of crankcase below mounting tabs: 1.7" (43mm)
Width between mounting tabs: 2.4" (61mm)

Carburetor Settings
High Speed Needle: Two turns open from fully closed
Medium Speed Needle: One turn open from fully closed
Idle Mixture Control: At basic position when engine leaves factory

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