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O.S. - OSMG0982 OSM34820 34820 531028019935 4531028019935
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O.S. 81FS-a Alpha Series Ringed 4-Stroke w/Pump
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O.S. 81FS-a Alpha Series Ringed 4-Stroke w/Pump
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Instruction Manuals: Manual 1 (2.4 MB)
Tower Catalog Page: 169

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Tech Notes
This is the glow powered O.S. FS81-a P 4-Stroke Aircraft Engine
with the PD-08 Fuel Pump.


Same mounting dimensions as the O.S. Max FS-70 Surpass II
Ideal fit for 60 size planes
Fuel pump delivers fuel consistently to the engine at all times
regardless of aircraft's attitude and fuel level
Specially designed lubrication system eliminates need for crankcase
61R carburetor with attached regulator
F5030 muffler with rubber O-ring in multi position manifold to help
prevent oil leakage


O.S. FS81-a P 4-Stroke Aircraft Engine, carburetor, muffler, header,
type F glow plug, PD-08 pump and instruction manual


Fuel: 10%-20% nitromethane with 18% lubricant. Synthetic, castor, or
a synthetic/castor lubricant blend may be used.
NOTE: Certain four-cycle fuels cannot be used due to low oil content.
However, SOME four-cycle fuels such as the Wildcat 4-Cycle 15%
(CATP9109) may be used due to its 18% oil content.
When choosing fuels for this engine, be sure to select a fuel with
at least an 18% lubricant content.
Propeller: Sport and aerobatic scale 13x7-9, 14x6-7


Displacement: 0.809 cu in (13.26cc)
Bore: 1.091" (27.7mm)
Stroke: .866" (22mm)
Weight with Muffler: 22oz (624g)
Practical RPM Range: 2200-10,000
Output: 1.28 PS, 1.28 HP @ 10,000 RPM
Height from Bottom of Mounting Tab to Top of Crankcase: 3.8" (97mm)
Width of Crankcase below Mounting Tabs: 1.6" (40mm)
Center of Mounting Holes Same Side: .83" (21mm)
Center of Mounting Holes Opposite Side: 2" (50.8mm)
Center of Front Mounting Hole to Drive Washer: 2.2" (55.5mm)
Center of Rear Mounting Hole to Drive Washer: 3" (76.2mm)
Center of Crankcase to Center of Needle Assembly: 1.4" (35.6mm)
Center of Crankcase to Outer Edge of Needle Assembly: 1.8" (45.7mm)
Muffler Angle in Relation to Engine: 10

Carburetor Needle Settings: Needle Valve, 1-1/2 - 2 turns open from
fully closed

jxs 10/02/09

– 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 Glow Powered O.S. FS81-a P 4-Stroke Aircraft Engine with Pump. FEATURES: Same mounting dimensions as FS-70 Surpass, PD-08 pump for consistent fuel delivery F5030 muffler, multi position manifold, type F glow plug, 61R carburetor with integrated regulator REQUIRES: Fuel, 10-20% nitro w/18% lubricant, prop, field equipment

Accessories for the O.S. 81FS-a Alpha Series Ringed 4-Stroke w/Pump

Primary Accessories   Building & Field Equipment Optional Accessories
  Special Stock Number Product Description Parts Saver Eligible Tower's
Low Price
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 LXRXC4 Tower Hobbies TOWER Power 10% Airplane Fuel Quart
Qty Discount Available
9.19   In Stock
Subtotal for this Group of Accessories: 9.19  

Primary Accessories   Building & Field Equipment Optional Accessories

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