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O.S. - OSMG1980 OSM18647 18647 531028021716 4531028021716
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O.S. 91HZ-R 3C Speed Red Helicopter Engine
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O.S. 91HZ-R 3C Speed Red Helicopter Engine
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On-line Videos: Video 1 (6.3 MB)
Instruction Manuals: Manual 1 (1.6 MB)
Tower Catalog Page: 168

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Tech Notes
This is the O.S. Engines 91 HZ-R 3C Speed Helicopter Engine in Red.

****** Because of the competition nature of this engine,******
******it is NOT covered by the O.S. 2 Year Warranty.******


Designed for all-out F3C competition
Demand Regulator System ensures consistent fuel delivery from full
to empty
170 exhaust timing for optimal horsepower and stable hovering
Newly designed combustion chamber shaped to match the big bore
carburetor and advanced exhaust cylinder timing
0.44" (11.2mm) Big Bore 61G carburetor for greatest power needed
for F3C maneuvers
Crankshaft counter-weight reduces vibration at high RPM


91 HZ-R 3C Speed Helicopter Engine with #8 Glow Plug, Aluminum Check
Valve, 0.008" (0.2mm) Head Gasket,, Aluminum Control Arm, two
Needle Adjusting screws and Instruction Manual


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

jxs 04/08/11

– If you need more information, use these O.S. resources –
Click Here: Manufacturer's Product Web Page
Email: enginesupport@hobbico.com
Web Site: http://www.osengines.com/
Phone: 217-398-8970
  Postal Address:

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Accessories Needed
This is the O.S.Speed .91HZ-R F3C Competition Heli Engine in Red. FEATURES: Big bore carb, suited for 3C precision manuevers, demand regulator system, forged steel crankshaft counter weight to lower vibration, #8 plug REQUIRES: 10%-30% nitro fuel w/at least 18% lubricant content, glow starter & field equipment

Accessories for the O.S. 91HZ-R 3C Speed Red Helicopter Engine

Primary Accessories   Building & Field Equipment Optional Accessories
  Special Stock Number Product Description Parts Saver Eligible Tower's
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 LXK129 Great Planes Silicone Fuel Tubing Standard 3'
Qty Discount Available
2.99   In Stock
 LXK134 Great Planes Ultra Precision Fuel Filter
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3.79   In Stock
 LXL387 Hobbico 4-Way Wrench w/Plug Storage
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4.99   In Stock
Subtotal for this Group of Accessories: 11.77  
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Primary Accessories   Building & Field Equipment Optional Accessories

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