O.S. 56FS-a Ringed 4-Stroke w/Muffler

Tower Stock# LXRUF7  •  Manufacturer Stock# 34300
O.S. 56FS-a Ringed 4-Stroke w/Muffler (large view)
Notes from our tech department:
This is the O.S. FS56-a Four Stroke Engine.
Same mounting dimensions as the FS-52 Surpass.


Improvements over the original FS series include;
Elimination of Crankcase venting-excess crankcase oil is now drawn
into the Rocker Cover, injected back into the combustion chamber.
Stronger Connecting Rod, Wristpin and Valve assembly
Extended intake tube on Carburetor restrains the reverse flow of
the air/fuel mixture
Decreased width Camshaft housing for less interference with sides
of aircraft nose section
F-4040 muffler with adjustable offset and outlet direction for
easier cowl installations
40NA two needle Carburetor


O.S. Max FS56-a Four-Stroke Engine with F-4040 muffler, type "F"
header pipe, glow plug, instruction manual


Fuel: 5-20% nitro with 18% lubricant content
Propeller: Sport & aerobatic; 13x6, 12x6-8
Scale; 13x6-7, 12x6-8
(break-in engine with prop intended for use on model)
Electric starter, glow starter and field equipment


Displacement: 0.569 cid (9.32cc)
Bore: .945" (24mm)
Stroke: .811" (20.6mm)
Practical RPM: 2,400-13,000
Output: 1.0 PS, 0.99 HP
Weight: 14.8oz (419g)
Crankshaft Size: 1/4-28
Break-in Needle Valve Settings: 2-2.5 turns from fully closed
Distance Between Mounting Holes Same Side: .69" (17.5mm)
Distance Between Mounting Holes Opposite Side: .16" (44mm)
Height from Crankshaft Center to Rocker Cover: 3.3" (84mm)
Distance from Crankcase Center to Prop Hub: 2" (50.8mm)
Distance from Crankcase Center to End of Crankshaft: 3.5" (88mm)
Distance from Crankcase Center to Throttle Lever Center:1.3" (32.5mm)
Width of Crankcase Below Mounting Tabs: 1.3" (34.1mm)
Angle of Muffler in Relation to Engine: 11

Needle Settings: High Speed: 2.5 - 3 turns out from fully closed
Low Speed: Flush with carb body

jxs 4/19/07
updt jxs 8/27/07
updt lmm 3/31/09

See Tower Catalog page 175.
Easy RC: Engines
Review #1
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