O'Donnell SS .21 User manual

1
ENGINE
E N G I N E

2
TABLE OF CONTENTS
Thank you for purchasing the O’Donnell SS .21 engine. Many years
of engine expertise were used to develop an engine with maximum
performance and reliability.This engine was manufactured using the
highest quality standards, materials and manufacturing processes.
When properly used and maintained, it will perform at the highest
level of racing. Carefully read through the entire instruction manual
before starting your SS .21 engine.
Safety Precautions .......................... 3
Important Information...................... 4
Fuel ................................................. 5
Fuel Tubing...................................... 5
Fuel Filter ........................................ 5
Air Filter........................................... 6
Glow Plug........................................ 6
Tuned Pipe ...................................... 7
Carburetor Restrictors..................... 7
High Speed Needle......................... 8
Low Speed Needle.......................... 8
Throttle Stop Screw......................... 8
Factory Carburetor Settings ............ 8
Priming the Engine.......................... 9
Engine Break-In ............................ 10
Engine Maintenance ..................... 12

3
SAFETY PRECAUTIONS
• Model engine fuel is poisonous. Make sure you read and follow all
of the precautions on the fuel container.
• Keep fuel out of the reach of children.
• Model engine fuel is flammable and when ignited has a flame
that is difficult to see. Avoid sparks, flames, smoking or any other
ignition source when fuel is near.
• The engine emits harmful fumes just like a real vehicle. Do not
operate the engine indoors.
• The engine and its exhaust can become very hot during operation.
Avoid touching these parts during use and until they have cooled
down completely.
• The engine and exhaust produce quite a bit of noise. Do not run
your vehicle when or where it can disturb others.
• Avoid running the engine in cold weather.Running the engine in cold
weather can result in premature wear and poor performance.

4
IMPORTANT INFORMATION
• Make sure you properly tighten the flywheel/collet onto the engine.
We recommend using a flywheel wrench and a 10mm socket. DO
NOT put something in the exhaust to prevent the engine from
turning over.
• Make sure you keep your vehicles fuel tank free of dirt and debris.
• Make sure your vehicle’s clutch is in good working order before
installing it onto the SS .21. Periodically check your clutch to
ensure optimal performance.

5
FUEL
• We recommend O’Donnell 20% or 30%
racing fuel be used whenever possible. If
at any time during the life of the engine
you change fuel, either the percentage of
nitromethane or brand, we recommend
that you set the carburetor needles back to
the stock settings to help prevent possible
damage or premature engine wear.
• Whenever possible, do not allow the fuel
container to sit in direct sunlight or opened.
Always close the container promptly after
each use. Do not store on a concrete floor.
Doing so will decrease the quality of the
fuel and could cause the engine to perform poorly.
• We recommend that you install new fuel tubing on your vehicle
before installing the SS .21.This will help prevent problems related
to old or torn fuel tubing.
• We highly recommend a quality fuel filter be used between the
vehicle’s fuel tank and the SS carburetor. This will help keep out
dirt and debris that could be detrimental to the life of the engine.

6
AIR FILTER & GLOW PLUGS
• It is very important that you use a quality air filter like the O’Donnell
ODOC1525 air filter. It is also just as important that you properly
maintain it. Using an air filter that is overly dirty, torn, improperly
oiled or worn out could allow dirt to be ingested, which will cause
premature wear and failure. We recommend that you clean and
re-oil your air filter regularly and always use a quality air filter oil.
• The SS .21 comes with an O’Donnell 97T glow plug. After
extensive testing, Steve O’Donnell has found that this plug gives
you maximum performance and superb durability.
• We recommend that you always keep a spare
O’Donnell 97T (ODOG0497) on hand so that you
can replace the plug when needed.You can check
your glow plug by pulling it out of the engine and
install it onto a charged glow starter. If the glow
plug glows bright orange it should still be good. If
it does not glow it is time to replace the plug.You can also check to
make sure that the coils are not distorted. If the coils are distorted,
replace the plug.
• Important: If you change plug types or brands, you will have to
re-tune your engine.

7
TUNED PIPE
CARB RESTRICTORS
• The SS .21 comes with a 7mm restrictor installed in
the carburetor.
• For increased performance, install the included 8mm
restrictor. The engine will need to be re-tuned after
changing the carburetor restrictor (richer mixture).
After extensive testing Steve O’Donnell has
developed the R2 tuned pipe for the SS .21. The
R2 tuned pipe helps the engine achieve maximum
performance, with a smooth, broad power band.
ODOG8000

8
NEEDLE SETTINGS
The high speed needle (A) controls the
amount of fuel entering the engine when
the carburetor is fully open. Turning the
high speed needle counterclockwise
(richer) allows more fuel to enter the
engine. Turning the high speed needle
clockwise (leaner) allows less fuel to
enter the engine.
The low speed needle (B) controls the amount of fuel entering
the engine during idle to the mid range. The low speed needle
affects your low end power. Turning the low speed needle
counterclockwise (richer) allows more fuel to enter the engine
and turning the low speed needle clockwise (leaner) allows less
fuel to enter the engine.
The throttle stop screw (C) adjusts the idle of the engine. Turning
the stop screw clockwise will increase the idle. Turning the stop
screw counterclockwise will lower the idle. Setting the idle too high
can cause damage to the clutch. Setting the idle too low can cause
the engine to stall frequently.
The factory needle settings for the SS .21 are:
High Speed: 2-1/2 turns out
Low Speed: 1-1/2 turns out

9
PRIMING THE ENGINE
We recommend that you prime your engine before starting it. While
holding the throttle open, place your finger over the muffler outlet
on the tuned pipe and turn the engine over using a starter box for
3–5 seconds or until fuel reaches the carburetor. DO NOT install
your glow starter during priming. Turn your transmitter and receiver
on, install your glow starter and then start your engine. Do not hold
the throttle wide open while starting, use only 1/4-throttle. Allow the
engine to idle for 10–15 seconds before increasing the throttle. If
the engine does not start within 8–10 seconds, remove the glow
plug and check that it and your glow ignitor are working properly.
Note: If you are having problems tuning your engine, we recommend
that you return the needles to the factory settings and make small
tuning adjustments until you achieve the optimal settings for the
particular conditions.
To reset the needles to factory settings, gently close (clockwise) the
needles. Then open (counterclockwise) the needles the designated
number of turns.
Important: Make sure when closing the needles you do not
overtighten. Overtightening the needles can cause damage to
the carburetor.

10
ENGINE BREAK-IN
It is critical that you properly break-in your SS .21. Proper break-
in will help ensure optimal fit between critical engine components
and help prevent premature wear. Proper break-in will help obtain
maximum performance.
• It is recommended to NOT run the body on your vehicle during
break-in.
• DO NOT run the engine at full throttle until the break-in procedure
is complete and the needles are set for your current conditions.
• We DO NOT recommend that you idle your engine on a starter
box for break-in.
• Do not allow the engine to run out of fuel during break-in. This will
cause the engine to lean out possibly causeing engine damage.
• We highly recommend the use of a quality temperature gauge like
the O’Donnell TGX1 (ODOP0900) to monitor engine temperature.
The high and low speed needles are preset at the factory. The
factory needle settings are a safe (rich) starting point.
Find a large, flat, open area to perform the break-in procedure.
Make sure you are in an area where you will not disturb others or
have to worry about traffic.
When leaning the engine during break-in, only
make adjustments of 1-hour increments. This will
help prevent over leaning the engine during break-
in and causing damage to your engine.
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12
93
1 hour = 1/12 turn