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OS FS-120 Surpass w/o Pump


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OS FS-120 Surpass w/o Pump
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More like this... 4-C Glow Aircraft Motors 1.10 to 1.50
But only from... OS ENGINES

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1.218 cu in
1.197 in
1.083 in
30.5 oz
1.9 @ 11,000
2,000 to 11,000 rpm
RPM Range:
Crankshaft Thread:


OS developed the Surpass Series of 4-cycle engines for discerning fliers who demand more power. All Surpass engines feature a helix gear driven camshaft on the front end and newly designed updraft carbs in the back. Enlarged intake valves and stronger working parts yield superior compression and improved output in the power stroke. OS Surpass 4-cycle engines provide the best performance for your plane, regardless of scale or flying style.

The FS-120 Surpass E is the basic suction-feed version of the FS-120 series, without fuel pump or pressure regulated carburettor, but with all the other quality features found in the FS-120S series engines, which, at 20cc, are the largest single-cylinder engines in the OS four-stroke range. Excellent for sport flying with large models and for scale models where the fuel tank can be located normally. Muffler and glow plug included.

   This is one of the O.S. Surpass series of 4-stroke model engines.           
The Surpass series is the 2nd series of 4-stroke engines (The 1st series was
the FS series, discontinued and replaced by the Surpass series around 1986-7).
"Surpass" refers to the fact that this series gained 30% more power than the
previous FS series.

FEATURES: 30% larger Intake Valves than the FS series
Ringed Piston
Rear-mounted updraft Carburetor
Helix Gear-Driven Camshaft
Ball Bearing-Supported Camshaft and Crankshaft
Covered under 2-YEAR WARRANTY

INCLUDES: One Assembled FS-120 Surpass w/Carb and No Pump
One #F Glow Plug
One Exhaust Header
One Exhaust Muffler
One Choke Valve Extension
One Set of Instructions, Poster, and Decals
(Wrenches, Choke Valve Extension, and Mounting Template Are No
Longer Included per O.S.)

REQUIRES: Fuel: 5%-15% nitromethane with 18% lubricant. Synthetic, castor, or
a synthetic/castor 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 because it has 18% oil content.
When choosing fuels for this engine, the modeler must be sure to
select a fuel with at least an 18% lubricant content.
Starting and Field Equipment
Propeller (see SPECS)

SPECS: Bore: 31mm (1.22")
Stroke: 27.5mm (1.08")
Power Output: 1.9 PS, 1.87HP at 11,000 RPM
Weight-Without Muffler: 30.5oz (864g)
Weight-With Muffler: 33.3oz (944g)
Practical RPM Range: 2,000 - 11,000 RPM
Crankshaft Thread Size: 5/16-24
Valve Clearance: Between .04mm and .1mm (or between .0015" and .004",
measured between the valve tip and rocker arm)
Length: 104mm (4.09") from backplate to the front of drive washer
Width: 47mm (1.85") width of engine neglecting the mounting flanges
58mm (2.28") distance between the mounting hole centers
Height: 138.5mm (5.45")
Suggested Prop(s): 13x11, 13x12, 14x10, 14x11, 15x8, 16x6, 16x7, 17x6
Construction: Aluminum and Aluminum alloys

Needle Settings: High Speed: 2.5 - 3 turns out from fully closed
Low Speed: Edge of larger sleeve centered, looking
down the neck of the carb

COMMENTS: Some differences between 4-Stroke and 2-Stroke engines.
4-strokes are quieter.
4-strokes get better fuel economy.
2-strokes generate more RPM (11,000-13,000 RPM with prop
while 4-strokes rev to around 9,500 RPM)
4-strokes generate much more torque and will swing a larger prop.
4-strokes have a realistic sound, like a real aircraft engine.
JBN 7/20/93
updt lmm 3/31/09
4531028017108 4531028017108