O.S. engine FS-70S User Manual

INSTRUCTIONS FOR
0.S.
FS-'70S
FOUR
STROKE
CYCLE
ENGINE
IMPORTANT: Before attempting to operate your FS-705,
please read through these instructions so as to familiarize
yourself with the controls and other features of the engine.
Also, pay careful attention to the recommendations con-
tained in the “Safety Instructions and Warnings” leaflet
enclosed.
INSTALLATION
Use sturdy engine mounting beams: i.e. at least as strong as
would be used for a two-stroke engine of 15cc, or greater,
displacement. Make sure that these beams are firmly
integrated with the airframe, reinforcing the internal sur-
rounding structure as necessary to absorb vibration. Engine
installation should be made in such a way that basic main-
tenance, including the checking and adjustment of valve
clearances, can be conveniently carried out. As an aid to
aligning the engine on its mounting beams, a simple mount-
ing hole template is supplied with the engine.
As an alternative to horizontal beam mounting, a special
O.S. radial motor mount is available, as an optional extra
part, for use where firewall mounting is required.
SILENCER ASSEMBLY
Installation procedure is as follows.
1. Screw the exhaust header pipe into the exhaust port
until it “bottoms”, then unscrew it just sufficiently to
achieve the required exhaust outlet angle. Secure the
pipe in this position by tightening the locknut firmly
against the cylinder head with the wrench supplied.
2. Screw the silencer onto the end of the header pipe and
tighten locknut firmly.
Note: It is advisable to apply silicone sealant at the joints to prevent
leakage of exhaust gas and loosening of nuts.
lg 1 aaa An, hie le! alate
CARBURETTOR THROTTLE
The needle-valve and throttle lever locations are inter-
changeable by reversing the carburettor. This can be done
as follows:
Remove the carburettor carefully by unscrewing the two
screws which secure both carburettor and choke valve. (See
Photo
1.)
If
the
carburettor
remains
difficult
to
remove,
slightly
loosen
the
two
screws
which
secure
the
intake
pipe
to the cylinder head.
After reversing the carburettor, re-insert it into the intake
pipe gently, taking care not to damage the O-ring in the
carburettor by using force.
Intake pipe
Ha Nid ring
Carburettor
fixing screws
Set screw
i Mee lever
Hexagon nut
Cap screw
Choke rubber pad
Photo 1
CHOKE VALVE |
The FS-70S is equipped with a spring-loaded choke valve.
The choke valve operating lever can be located right or
left by transposing the hexagon nut and cap screw.
After
mounting
the
engine
in
the
model,
secure
the
L-shaped
choke
rod
by
tightening
the
set-screw.
If
the
rod
supplied
is
too
long,
reduce
it
to
the
required
length.
If
the
rod
length
is
more
than
40mm
(1%
in.)
its
outer
end
should
be
supported
to
avoid
vibration.
SPECIFICATIONS
11.50 cc (0.702 cu.in.)
25.8 mm (1.016 in.)
22.0 mm (0.866 in.)
2,000 ~ 12,000 r.p.m.
Displacement
Bore |
Stroke
Practical R.P.M.
Output 1.1 BHP/11,000 r.p.m.
Weight 570 g (20.1 oz.)
FUEL TANK
The suggested fuel tank size is 270cc or 9% oz. This will
give approximately 12 minutes running time when some
part-throttle operation is included. Locate the fuel tank so
that the centre line of the tank is 10 to 15mm below the
centre line of the needle-valve.
Note: If the model is left unattended
with the fuel tank filled, fuel
may flow into the carburettor,
causing it to “flood” and
making the engine difficult to
start. Take appropriate action
to prevent this.
FUEL
The FS-70S runs on standard commercially available model
glowplug engine fuel. Fuels containing castor-oil and/or
synthetic lubricants are acceptable, but for the best per-
formance and reliability, a fuel containing 5 — 15% nitro-
methane is recommended.
For consistent performance and long engine life, it Is
advisable to use good quality fuel containing 16 to 20%
lubricant.
(The carburettor is adjusted with a fuel containing 20%
lubricant when the engine leaves the factory.)
(| Centre line
nla
GLOWPLUG
An O.S. Type “F” glowplug is fitted to the engine.
With a four-stroke engine, ignition of the fuel charge takes
place at every fourth stroke of the piston instead of every
second stroke. Because of this, some conventional two-
stroke glowplugs will not suit this engine. For general use,
the special O.S. Type F glowplug is recommended.
PROPELLER
The choice of propeller depends on the design and weight
of the model and on the type of flying envisaged. Deter-
mine the best size and type after practical experiment. As
starting points, suggested propellers are listed below.
For sport & stunt
models
11x8
~
9,12x7
~8
12%
XG
13%x8, 14x7, 11x7 (3-blade)
For
scale
models
12x8
(3-blade),
12%x7
(3-blade)

O.S. engine FS-70S Specifications

General

Brand	O.S. engine
Model	FS-70S
Category	Engine
Language	English

Summary

Installation and Setup

INSTALLATION

Guidelines for mounting the engine securely in the airframe and ensuring accessibility.

SILENCER ASSEMBLY

Steps to correctly screw and secure the exhaust header pipe and silencer.

CARBURETTOR THROTTLE

Instructions for reversing the carburettor for optimal positioning and choke lever.

CHOKE VALVE

How to adjust the choke valve lever and rod for operation, ensuring secure mounting.

Engine Specifications and Fuel

SPECIFICATIONS

Technical details like displacement, bore, stroke, output, and weight.

FUEL TANK

Recommended fuel tank size and placement relative to the engine's center line.

FUEL

Details on recommended fuel types, nitro content, and lubricant levels for performance.

GLOWPLUG

Information on the recommended O.S. Type "F" glowplug for four-stroke engines.

Operation and Running-in

PROPELLER

Guidance on selecting and mounting the correct propeller for the engine.

STARTING

Step-by-step instructions for both electric and hand starting the engine safely.

RUNNING-IN

Procedure for the initial break-in period to ensure engine longevity and performance.

Carburettor Adjustments and Maintenance

ADJUSTING THE CARBURETTOR

How to adjust needle-valve, mixture control, and throttle stop screws for optimal performance.

REALIGNMENT OF MIXTURE CONTROL VALVE

Resets the mixture control valve to its factory specified position for correct adjustment.

CARBURETTOR CLEANLINESS

Importance of keeping carburettor orifices clean for reliable engine performance.

Advanced Maintenance and Parts

VALVE CLEARANCE ADJUSTMENT

Procedure to check and adjust valve clearances when the engine is cold.

NEEDLE VALVE EXTENSION

How to fit an extension for external adjustment of the needle valve.

CARE AND MAINTENANCE

General advice on engine care, cleaning, and long-term storage to prevent damage.

PARTS LIST

A comprehensive list of available spare parts with their corresponding code numbers.