MDS 18 FS Pro, 28 FS Pro, 38 FS Pro, 40 FS-1 Pro, 48 FS Pro Instructions Manual

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Engine Operating

I n s t ru c t i o n s

Pro Series

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Congratulations on your purchase
of an MDS engine. MDS engines
are noted for their excellent power,
rugged reliability, and efficient
operation. All MDS engines are
precision machines and should be
handled with care. The following
information and recommendations
are presented to help you become
more familiar with the operating
characteristics of your new MDS
engine. Please closely follow the
break-in procedures and maintenance
instructions. Also, be sure to read
the enclosed safety instructions and
warranty information.

Step 1. Assembly

Inside the MDS engine box you should find the following items:

1. Engine

2. Aeromix™carburetor with O-rings (may be pre-installed)

3. Muffler (style may vary depending on engine)

4. Complete accessory and tool set with muffler mounting
hardware (included tools may vary with different engines)

• Instructions and warranty card

Photo 1

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1

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2

4

To assemble your new engine, please follow these simple steps:

Step 1A.

Note: Refer to the exploded view of the engine on the last page to
identify the parts discussed in the text.

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1. Remove the individual plastic bags from the box and place
them on a table or workbench. Remove the engine from its
plastic wrapper. Note: Some engines may already have the
carburetor installed, but make sure that the carb retaining bolt
is tightened.

2. Inspect the carburetor retainer to insure that the curved portion
of the carburetor retainer drawbar matches the inside wall of the
air intake port. If it does not, simply place it in position with
your finger. Next, remove the tools from their protective
wrapper. You will need the Allen wrench to tighten the
carburetor retainer. (As noted above, some engines come
with the carburetor already mounted.)

Photo 2

Carb
Retaining
Bolt

O-Ring

VERY IMPORTANT:

An improperly installed O-ring

may lead to unreliable performance.

3. Remove the O-ring from the parts bag. Install the O-ring into
the cavity of the air intake port of the crankcase, as shown in
Photo 2, making sure that the O-ring is seated evenly at the
bottom of the cavity and cannot come in contact with the
engine crankshaft. The second O-ring is a spare. Insert the
carburetor into the intake port.

Step 1B.

4. The carburetor is correctly positioned when the throttle arm is
located on the right side of the engine when viewed from the
rear. Please note the carburetor can be rotated 180 degrees for
those applications that require the needle valve to be on the
opposite side. Tighten securely with the appropriate wrench
while applying slight pressure on the carburetor to compress the
O-ring. This will create a good, airtight seal. CAUTION: Do not
overtighten, as doing so will damage the carburetor body.

Step 2.
Break-In Procedures

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Prior to starting your new MDS ringed or ABC engine, it’s
important that you first understand the break-in procedure for
your type of engine. Most modelers prefer to do this while the
engine is installed in the aircraft or heli. With today’s tolerances
and available metallurgy, the break-in time has been shortened to
the point that bench running is not necessary. If you’re not sure
whether your engine is ringed or ABC, simply look through the
exhaust port and move the piston until you can see the top
portion. If it’s ringed, you will see a dark metal ring approximately
1/8” from the top. If it’s ABC, the piston will be one piece and all
the same color of the piston.

Ringed Engine Break-In

Excessive heat build up during the first few runs can damage the
ring and cylinder. A very rich needle setting is required to keep the
engine cool while the ring seats. To set a “rich” mixture, lean the
high-speed needle for a good 2-cycle, then richen the high-speed
needle counter clockwise a full turn. While running rich, the
engine will create quite a bit of smoke and the exhaust will be very
oily. After a couple of tank fulls at a rich needle setting, you can

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begin leaning the high-speed needle a few clicks at a time for best
performance, keeping in mind that a too lean setting at any time
can damage the ring and cylinder.

ABC Engine Break-In

Breaking-in your ABC engine requires the same basic procedure as
with the Ringed engine, except for a couple of minor differences.
The first couple of runs should be at a slightly rich setting, close to
normal operating temperatures. Heat helps the piston seat in the
liner. Also, the time involved is shorter; most ABC engines can be
fully broken-in within 3 or 4 flights at a slightly rich setting.

Step 2A. Muffler Mounting

Remove the muffler from the plastic bag. The muffler mounting
bolts are located in the tool set, as are the tools to mount
the muffler.

Step 2B. Fuel Tank Placement

The location of the fuel tank can greatly affect the operation of
any engine. Whether mounting the engine on a test stand or in
your model, we suggest that you position the tank as close to the
engine as possible. The center line of the fuel tank should be as
close to level with the engine flange mounts as possible
(See diagram on next page).