Tower Hobbies .40 ENGINE Instructions For

Parts of the Carburetor:

INSTRUCTIONS FOR

®

®

.40 ENGINE

Please read and follow this instruction manual before operating your engine.

Thank you for purchasing this high quality Tower .40 engine. Your engine was
produced to exacting tolerances with state-of-the-art computerized machine
equipment using the finest materials and should provide consistent, reliable
service for many years. The new safety needle valve design feature of this
engine is a step forward in engine technology, offering safer operation than
conventional needle valve locations. The ABC construction and schnuerle porting
will provide you with performance to meet your sport flying needs, along with
easy starting and reliability. Like all model airplane engines, care must be taken
in operation as severe injury can result from improper or careless use. Please
read and understand the safety precautions and warnings in this manual before
operating this engine.

Pressure Fitting

Glow Plug

Important:

© Copyright, 1998

Cylinder Head
Crankcase

Needle Valve: The needle valve controls the
fuel/air mixture entering the carburetor.

Air Bleed Screw: The air bleed screw controls
the amount of fuel/air mixture entering the
carburetor while the engine is idling.

Idle Stop Screw: The idle stop screw controls
how far the throttle closes. We suggest that it
be set to allow the throttle to close completely
to stop the engine using the throttle trim on the transmitter.

Throttle Arm: The throttle arm is connected to the carburetor barrel and is operated by
the throttle servo. By moving the throttle arm,
the barrel can be opened and closed. This
adjusts the speed of the engine.

By loosening the nut next to the carburetor
body, the safety needle valve can be rotated.
By loosening the nut below the fuel inlet, the
inlet can be rotated. An optional straight
needle valve adapter (TOWG5260) is available
if the engine will be enclosed in a cowl.

How the Tower .40 Engine Operates:

The aluminum piston and chrome-plated brass cylinder are designed to have the proper
fit at normal operating temperature. As the engine warms up, each part expands,
producing the proper fit. If the fuel mixture entering the engine is wrong, the parts do not
expand properly. The engine will not run correctly and in some cases can be damaged.
The reason the fuel mixture is so important is that the fuel is a blend of oil (synthetic oil
and/or castor oil), nitromethane and alcohol; plus anti-wear and anti-foaming agents and
corrosion inhibitors. The Tower .40 engine will run best on fuel with a 5% to 15%
nitromethane content and a mixture containing castor oil or a castor-synthetic blend. The
nitromethane helps the alcohol burn better. The oil lubricates and cools the engine. So, if
the fuel mixture is not correct, the engine can overheat or will not get hot enough for the
cylinder to expand properly and provide maximum power.

Installation:

Loosen this
nut to rotate
the needle
valve.

Idle Stop

Screw

Needle

Valve

Air Bleed

Screw

Throttle Arm

Loosen
this nut to
rotate the

fuel inlet.

Carburetor

Muffler

Propeller Nut

Parts of the Engine:

Crankshaft: The crankshaft transforms the reciprocating motion of the piston into
rotational motion. The propeller is mounted on the portion of the crankshaft protruding
from the crankcase.

Propeller Nut: The propeller nut secures the propeller to the crankshaft.
Propeller Washer: The propeller washer provides a larger, stronger surface area to

apply pressure to the propeller.
Drive Washer: The drive washer is keyed to the crankshaft and is knurled on one face

to provide a good contact surface for the propeller.

Carburetor: The carburetor meters the amount of fuel and air that enters the engine.
Crankcase: The crankcase houses the internal parts.
Cylinder Head: The cylinder head is mounted on top of the crankcase. It provides a

seal at the top of the cylinder. The fins on the cylinder head provide a cooling surface.
The cylinder head also holds the glow plug.

Glow Plug: The glow plug provides the heat needed to ignite the fuel in the cylinder.
Muffler: The muffler quiets the exhaust exiting the cylinder.
Pressure Fitting: A tube is connected from the pressure fitting to the fuel tank. When

the engine is running, pressure from the muffler is used to pressurize the fuel tank.

Drive Washer
Propeller

Washer

Crankshaft

The beams the engine is to be mounted on must be rigid, parallel with each other and
the top surfaces in the same plane.

CORRECT

Top surfaces
of beams are

in the same

plane

Beams are parallel

INCORRECT

Top surfaces
of beams are

not parallel

Beams are not parallel

Top surfaces are not in

the same plane

Set the engine on the beams at the correct angle to the center line of the fuselage,
according to the instructions provided by the airplane manufacturer. Mark on the beam the
locations of the four mounting holes. If mounting the engine on wooden beams, drill four
7/64” holes through the beams perpendicular to the top surface of the beams. Secure the
engine to the beams with 4-40 screws, flat washers, lock washers and 4-40 nuts.

If mounting the engine on a metal or fiberglass
engine mount, follow the manufacturer’s
mounting instructions. If they did not provide
instructions, drill and tap the engine mount to
accept 4-40 screws and lock washers installed
through the engine mounting flanges and into
the engine mount.

Note: Some airplane kits require a slight amount
of right thrust. This is done by angling the
engine to the right to counteract the torque
factor of the propeller while making thrust.
Follow the kit manufacturer’s instructions to
incorporate the correct amount of right thrust
if required.

Muffler Installation:

Install the muffler on the engine
after the engine has been installed
in the airplane. Insert the two
muffler screws through the
crankcase and thread them into
the muffler. Tighten the muffler
screws, being careful not to strip
the threads in the muffler.

To adjust the exhaust outlet,
loosen the lock nut at the rear of
the muffler, then loosen the screw
at the front of the muffler. Rotate
the exhaust outlet away from the
airplane. Re-tighten the screw at
the front of the muffler just tight
enough to prevent the exhaust
outlet from rotating. Then tighten
the lock nut at the rear of the
muffler. If the screw is over­tightened the screw will break as
the muffler heats up and expands.

Pressure Line:

For the engine to operate properly
at any angle, the carburetor
requires constant fuel pressure.
When the engine is running,
pressure is created in the muffler
by the exhaust. Some of this
pressure is used to pressurize the
fuel tank. This pressure is provided
by a tube from the pressure fitting
on the muffler to the vent tube in
the fuel tank. Although not
absolutely necessary, pressurizing
the fuel tank with muffler pressure
will provide more consistent
running, and will help to maintain
more consistent fuel flow during
maneuvers. We recommend the
use of muffler pressure.

Fuel Line:

Connect a medium size silicone
fuel line from the fuel inlet on the
carburetor to the fuel pick-up tube
that is connected to the clunk in
the fuel tank. We suggest that a
fuel filter be installed in the fuel
line between the carburetor and
the fuel tank. The filter will prevent
any contaminants in the fuel from
clogging the carburetor.

Equipment Required to Operate the Tower 40 Engine

Muffler Screws

Loosen this nut

Rotate the exhaust outlet

Loosen this screw

From fuel

pick-up tube

in fuel tank

Fuel
Inlet

Glow Plug Wrench:

The glow plug will
eventually fail to
retain heat or it will
need to be removed
to clear a flooded
engine. We
recommend a Hobbico 4-Way
Wrench (HCAP2550) that can be
used to remove the glow plug and the
propeller nut.

Propeller: For "break-in" and most
trainer and sport airplanes, we
suggest a Top Flite 10x6 Propeller
(TOPQ5085). A 10x5 (TOPQ5080) or
an 11x4 Propeller (TOPQ5095)
may also be used.

Chicken Stick or Electric Starter: Again, if a
field box is used, we recommend a Tower
Hobbies Electric Starter (TOWP0500). If you do
not have a field box with a 12 volt battery, a
chicken stick can be used to flip the propeller
to start the engine.
Caution: never use your finger to flip the
propeller. If the engine should backfire, the
propeller could injure your finger.

Glow Plug Battery: For ease of operation and safety we
recommend a Hobbico Glow Plug Clip (HCAP2505) with the
self contained battery. If using a Tower Hobbies Glow Plug
Clip (TOWP1200) connected to a power panel on a field box,
make sure the wire lead is behind the propeller when
starting the engine.

Nuts
Lock

Washer

Washer

4-40

Screw

Rigid Beam

Attach to

pressure fitting

on muffler

From vent

tube in

fuel tank

Glow Plugs: For best
performance and sure-fire
starts, we recommend using
Tower Hobbies R/C Long Glow
Plugs (TOWG1001).

Fuel Pump: If you will be using a field box, we recommend a
Hobbico Electric Fuel Pump (HCAP3100) that can be mounted on the field box. If you
will not be using a field box, we recommend a Tower Hobbies hand Crank Fuel Pump
(TOWP1210).

High Quality Fuel: We
recommend two-stroke fuel

with 5% to 15%

nitromethane and a

mixture containing
castor oil or a castor­synthetic blend.
Tower’s own Tower
Power brand fuel is
recommended.