O.S. Engines FF-320 User Manual

It is of vital importance, before attempting
to operate your engine, to read the
general 'SAFETY INSTRUCTIONS AND
WARNINGS' section on pages 2-4 of this
booklet and to strictly adhere to the advice
contained therein.

Also, please study the entire contents of this
instruction manual, so as to familiarize
yourself with the controls and other features
of the engine.

Keep these instructions in a safe place so
that you may readily refer to them whenever
necessary.

It is suggested that any instructions supplied
with the aircraft, radio control equipment,
etc., are accessible for checking at the same
time.

Horizontally-opposed four-cylinder
overhead-valve four-stroke-cycle

CONTENTS

SAFETY INSTRUCTIONS AND
WARNINGS ABOUT YOUR O.S. ENGINE

INTRODUCTION, TOOLS AND ACCESSORIES

ENGINE PARTS NAME



INSTALLATION

PROPELLER

GLOWPLUGS

GLOWPLUG HEATING

FUEL AND LUBRICATION, STARTING

RUNNING-IN ("Breaking-in")

THROTTLE VALVE ADJUSTMENT

2-4

5

6-7

8-9

10-11

12

13-14

14-18

18-19

19-21

FLIGHT

CARE AND MAINTENANCE

VALVE CLEARANCE ADJUSTMENT

ENGINE EXPLODED VIEW

ENGINE PARTS LIST

CARBURETOR EXPLODED VIEW  &
PARTS LIST

O.S. GENUINE PARTS & ACCESSORIES

ENGINE THREE VIEW DRAWINGS

22

22

23-25

26

27

28

29

30

1

SAFETY INSTRUCTIONS AND
WARNINGS ABOUT YOUR
O.S. ENGINE

Remember that your engine is not a " toy ", but a highly
efficient internal-combustion machine whose power is
capable of harming you, or others, if it is misused or
abused. As owner, you, alone, are responsible for the safe
operation of your engine, so act with discretion and care at
all times.
If at some future date, your O.S. engine is acquired by
another person, we would respectfully request that these
instructions are also passed on to its new owner.

The advice which follows is grouped under two
headings according to the degree of damage or danger
which might arise through misuse or neglect.

WARNINGS

These cover events which might involve serious (in
extreme circumstances, even fatal ) injury.

NOTES

These cover the many other possibilities, generally less
obvious sources of danger, but which, under certain
circumstances, may also cause damage or injury.

WARNINGS

Never touch, or allow any object to come into
contact with, the rotating propeller and do not
crouch over the engine when it is running.

A weakened or loose propeller may disintegrate or be thrown
off and, since propeller tip speeds with powerful engines may
exceed 600 feet(180 metres) per second, it will be understood
that such a failure could result in serious injury, (see 'NOTES'
section relating to propeller safety).

Model engine fuel is poisonous. Do not allow it to
come into contact with the eyes or m o u th . A l w ays
store it in a clearly marked container and out of
the r e a c h o f children.

Model engine fuel is also highly flammable. Keep it
away from an open flame, excessive heat, sources
of sparks, or anything else which might ignite it.
Do not smoke or allow anyone else to smoke, near
to it.

Never operate your engine in an enclosed space. Model
engines, like automobile engines, exhaust deadly carbon­monoxide. Run your engine only in an open area.

Model engines generate considerable heat. Do
not touch any part of your engine until it has
cooled. Contact with the muffler(silencer),
cylinder head or exhaust header pipe, in
particular, may result in a serious burn.

2

NOTES

This engine was designed for model aircraft. Do not attempt to use it for any other purpose.

Mount the engine in your model securely, following the manufacturers' recommendations, using appropriate
screws and locknuts.

Be sure to use the silencer (muffler) supplied with the engine. Frequent exposure to an open exhaust may
eventually impair your hearing.
Such noise is also likely to cause annoyance to others over a wide area.

If you remove the glowplug from the engine and check its condition by connecting the battery leads to it, do not hold
the plug with bare fingers.Use an appropriate tool or a folded piece of cloth.

Install a top-quality propeller of the diameter and pitch specified for the engine and aircraft. Locate the propeller on
the shaft so that the curved face of the blades faces forward-i.e. in the direction of flight. Firmly tighten the propeller
nut, using the correct size wrench.

Always check the tightness of the propeller nut and retighten it, if necessary, before restarting the engine,
particularly in the case of four-stroke-cycle engines. If a safety locknut assembly is provided with your engine,
always use it. This will prevent the propeller from flying off in the event of a "backfire", even if it loosens. Also,
check the tightness of all the screws and nuts before restarting the engine.

If you install a spinner, make sure that it is a precision made product and that the slots for the propeller blades
do not cut into the blade roots and weaken them.

Discard any propeller which has become split, cracked, nicked or otherwise rendered unsafe. Never attempt to
repair such a propeller: destroy it. Do not modify a propeller in any way, unless you are h igh ly experienced in tuning
propellers for specialized competition work such as pylon-racing.

3

NOTES

Use an electric starter for this engine. The wearing of safety glasses is also strongly recommended.

Take care that the glow plug clip or battery leads do not come into contact with the propeller.
Also check the linkage to the throttle arm. A disconnected linkage could also foul the propeller.

After starting the engine, carry out any needle-valve readjustments from a safe position behind the rotating
propeller. Stop the engine before attempting to make other adjustments to the carburetor.

Adjust the throttle linkage so that the engine stops when the throttle stick and trim lever on the transmitter are fully
retarded. Alternatively, the engine may be stopped by cutting off the fuel supply. Never try to stop the engine
physically.

Take care that loose clothing (ties, shirt sleeves, scarves, etc.) do not come into contact with the propeller.
Do not carry loose objects (such as pencils, screwdrivers, etc.) in a shirt pocket from where they could fall through
the propeller arc.

Do not start your engine in an area containing loose gravel or sand. The propeller may throw such material in your
face and eyes and cause injury.

For their safety, keep all onlookers (especially small children) well back (at least 20 feet or 6 meters) when preparing
your model for flight. If you have to carry the model to the take-off point with the engine running, be especially
cautious. Keep the propeller pointed away from you and walk well clear of spectators.

Warning! Immediately after a glowplug-ignition engine has been run and is still warm, conditions sometimes exist
whereby it is just possible for the engine to abruptly restart if the propeller is casually flipped over compression
WITHOUT the glowplug battery being reconnected. Remember this if you wish to avoid the risk of a painfully rapped
knuckle!

4

INTRODUCTION

The O.S. FF-320 (PEGASUS320) is a horizontally­opposed four-cylinder overhead-valve four-stroke­cycle engine of 53.04cc (3.24cu.in) displacement.
The horizontally-opposed layout, typical of modern
light aircraft engine design, provides very smooth
running qualities and docile, trouble-free handling
characteristics.

TOOLS AND ACCESSORIES

The following tools and accessories are supplied with your
engine.

No.

Radial Motor Mount Set
Radial Motor Mount(installed on the engine)
Mount attachment Screws
Engine mounting screws (M5X25)

1

Lock washers (ø5)

2

Blind nuts (M5)

3

Set of leads for wiring glow plugs:

4

Leads for glow plug with clip

4-1

Lead for earth (ground)

4-2

Description

Quantity

1
4
4
4
4

4
1

No.

5

Woodruff key

6

Valve adjusting tool kit

7

Hexagonal (Allen) key (4mm)

8

Choke valve rod

9

Drain plug

4-2

4

4-1

Description

3

2

5

Quantity

1
1
1
1
1

8

9

6

7

1

Photo 1

5

ENGINE PARTS NAME

No.1 Cylinder

Photo. 2

Crankcase

No.3 Cylinder

Lock Nut

Propeller Washer

No.2 Cylinder

Propeller Nut

No.4 Cylinder

Front Housing

Breather Nipple

Exhaust Pipe

Carburetor

6

Choke V alve

Fuel Inlet

Intake Manifold

Photo. 3

Rocker Cover

Drain Nipple

Rear Housing

Cylinder Head

7

INSTALLATION

The FF-320 is equipped with a strong cast aluminum radial­type mount to enable it to be bolted securely to the firewall
(front bulkhead) of the aircraft.

It is essential that the firewall is strong and rigid (e.g. at
least 15mm thick) and firmly integrated with the structure of
the aircraft.

In the interests of scale appearance, the engine should be
installed with the carburetor below the crankcase so that
the exhaust pipes point downwards.

Center mark

M5 Blind nut

Center mark

Needle-valve extension

The needle-valve with this engine is designed to incorporate
an extension so that, when the engine is enclosed within the
fuselage, the needle-valve may be adjusted from the
outside. An L-shaped rod, of 1.6-1.8mm dia. and



appropriate length, should be inserted into the needle's
center hole and secured by tightening the set-screw in the
needle-valve knob with the small Allen key provided. For
longer extension, it is recommended to use the extension
cable with the engine, together with the knob and support
hook also. For this purpose, Needle Valve Extension Cable
Set (Code No. 72200080) is available as an optional part.

Do not use an excessively long unsupported extension as
this may vibrate and cause the needle-valve setting to vary
or even damage the needle-valve thread. Always provide a
suitable support at the outer end.

M5x25 screw

Firewall

5 Lock washer

At least 15mm (0.6")
rigid hard wood

Fig. 1

Choke valve

The choke valve operating lever can be located rught or left
by reversing the hexagon nut and cap screw.

Unscrew the cap screw while holding the hexagon nut with
6mm wrench, and re-fit the lever to required location.

If the rod is too long, reduce it to required length.
A needlessly lengthy rod may vibrete. The rod should be as

short as possible or have its outer end supported.

Set-screw

Cap screw

Fig. 3

Set-screw

Set-screw

Hook

Needle

Cable

Knob

Fig. 2

8

Exhaust pipe adjustment

The direction of the exhaust
pipes may be altered in
accordance with individual
installation requirements. The
angle is easily adjusted by
loosening the nut that secures
the exhaust pipe to the cylinder
head. Use the 12mm wrench
supplied.

12mm wrench

Loosen

Lock nut

Exhaust pipe

Fig. 5

Tighten

Carburetor cleanliness

It is recommended that the fuel is passed through a filter
when the tank is filled and that a good in-line filter is
installed between the fuel tank and carburetor.

Choke lever

Hex. nut

Choke rubber pad

Fuel inlet

The fuel inlet nipple on the carburetor can be adjusted to the
most suitable position for connecting to the fuel delivery tube
from the tank. Slacken the needle-valve holder with the 8mm
wrench provided, reset the inlet nipple at the required angle
and re-tighten.

Fuel inlet

Slacken with 8mm wrench

Needle-valve

Fig. 4

Occasionally remove the needle-valve holder from the
carburetor and rinse out the locaions shown in Fig. 6 and
Fig. 7 with methanol or fuel. Be careful not to lose the
gasket when removing the needle-valve holder from the
carburetor.

Fig. 6

Dirt and fibrous matter
mostly accumulate here.

Squeeze bottle

Dirt and fibrous matter
mostly accumulate here.

Needle-valve holder

9

Fig. 7

PROPELLER

The choice of propeller depends on the design and weight of
the aircraft and on the type of flying in which you will be
engaged. Determine the best size and type after practical
experimentation. As a starting point, refer to the props listed in
the accompanying table. Slightly larger, or even slightly
smaller, props than those shown in the table may be used, but
remember that propeller noise will increase if blade tip velocity
is raised, due to higher rpm or if a larger-diameter / lower-pitch
prop is used.

Warning:
Make sure that the propeller is well balanced. An

unbalanced propeller and / or spinner can cause serious
vibration which may weaken parts of the airframe or
affect the safety of the radio-control system.
DO NOT forget the WARNINGS and NOTES on propeller
and spinner safety given on pages 2,3 and 4.

PROPELLER & SPINNER ATTACHMENT

There is a risk, particularly with powerful four-stroke engines,
of the propeller flying off if the prop nut loosens due to
detonation ("knocking") in the combustion chamber when the
engine is operated too lean, or under an excessively heavy
load.

Obviously, this can be very hazardous. To eliminate such
dangers, the O.S. Safety Locknut Assembly was devised.
Install this as follows:

1.

Ream the propeller shaft hole to 12mm bore with an
appropriate reamer, checking that the hole is exactly
centered.

To be equal

Fig. 9

Type

Sport/Scale

2.

Install the prop to the engine shaft, followed by the retaining
washer and prop nut and tighten firmly with a 17mm
wrench. (not supplied).

3.

Add the special tapered and slotted locknut and secure
with a 12mm wrench while holding the prop nut with the
14mm wrench. (not supplied).

Propeller washer

Size (DxP

18x10-12, 20x8-10, 22x8

Use a propeller that has a
hub of more than 40mm dia.

)

Fig. 8

Fig. 10

10

To be equal

NOTE:
Make a habit of always checking the tightness of the
propeller before starting the engine. Remember that,
especially with wooden propellers, there is a tendency for
the material to shrink, or for it to be reduced by the
serrated face of the drive hub. Retighten the propeller nut
if necessary after loosening the Safety Propeller Locknut.
The locknut should be tightened firmly after retightening
the propeller nut.

Ream to 12mm dia.

Propeller nut

Locknut

Propeller washer

Locknut

Propeller nut

Drive hub

Back-plate of spinner

Drive hub

The Safety Propeller Locknut can
be used provided that the width is
between 21.5mm and 26mm.

11