A model engine makes
sounds that will tell you how it's performing. You'll have to
listen very carefully for them, recognize their message, and
make adjustments to the fuel control needle valves accordingly.
The mixture of fuel and air is controlled by the amount of fuel
metered by the needle valve.
SLOPPY RICH
MIXTURE running is characterized by a very slow, irregular,
sputtering exhaust sound. The exhaust gas will be very smoky
and contain many droplets of oil. This condition is good for
the very first initial run of a ringed or lapped engine as
it receives excess lubrication and runs cooler.
RICH MIXTURE
running is characterized by a slower, sometimes irregular,
sputtering exhaust sound. The exhaust gas will be smoky and
probably contain small droplets of oil. This condition is
good for Break-in since the engine receives excess lubrication
and runs cooler.
FOUR CYCLINGor
SLIGHTLY RICH is a rich type setting, but it is fast
enough to pull the airplane. This is the setting you normally
look for before launching the airplane because the engine
will run leaner when airborne.
PEAKED OR TWO
CYCLE. As the main needle is closed (clockwise), it reduces
the amount of fuel mixed with the air drawn into the engine.
At a specific point, which varies with each engine, air temperature,
altitude and relative humidity, the exhaust note will change
quickly into a smooth, powerful note. If the needle is closed
further, the note will stay smooth, but will weaken. The peak
occurs just at the break point from a rich setting and further
leaning will ruin the engine. A lean setting raises the engine
heat above the safe point, reduces lubrication, and destroys
glow plugs due to high combustion temperature. This is very
harmful to the engine and your investment. Learn to tune the
engine before flying. Remember, a little rich is always preferred
for long motor life.
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BENCH
BREAK-IN
NOTE THAT THE ENGINE MUST BE FIRMLY MOUNTED ON A SOLID TEST
STAND. DO NOT CLAMP ENGINE IN A VISE. Muffler may be used
during bench break-in.
The initial bench break-in period is
approximately 90 minutes (40 to 45 minutes bench and 45 minutes
airborne). During this time, use the recommended break-in
propeller and run the engine at a rich setting. It is best
to run the engine for about 10 minutes, then allow it to cool.
The heating and cooling aid break-in on lapped engines.
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Carbureted
engines:
1> Start the engine and run it at a sloppy rich full throttle
setting for approximately 3 minutes. Shut it off and allow
it to cool.
2>
Run it again at a rich full throttle for about 2 minutes,
then let it fast idle (about 3500 rpm's) for 30 seconds. Repeat
this sequence for about 20 minutes of running time. Be sure
the idle mixture setting is set very rich.
3> Increase the full open throttle time to about 3 minutes
followed by a 30 second idling period. Do this for an additional
for 20 minutes.
4> Install the engine in your aircraft. Using an normal
size prop, proceed as described in step 2 of "AIRBORNE BREAK-IN".
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Carbureted engines:
1> Start the engine and run it at a sloppy rich setting
for approximately 3 minutes. Shut it off and allow it to cool.
2>
Run it again at a sloppy rich setting for about 2 minutes,
then, lean the engine to a rich settng for 30 seconds, then
open the needle to a sloppy rich setting. Repeat this sequence
for about 20 minutes of running time.
3 > Increase the rich setting time to about 3 minutes followed
by a 30 second sloppy rich period. Do this for an additional
for 20 minutes.
4 > Install the engine in your aircraft. Using an normal
size prop, proceed as described in step 2 of "AIRBORNE BREAK-IN".
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AIRBORNE
BREAK-IN
1>We recommend some bench running before aircraft instalation.
BREAK-IN running should be done with the recommended propeller
at a sloppy rich setting. The needle valve should be set at
a point just into this range from a rich setting. Fly the
plane at maximum throttle for 2 minutes, then throttle back
for approximately 30 seconds. Repeat this sequence until approximately
45 minutes of accumulated running time has been obtained.
Additionally, certain maneuvers, such as "CUBAN EIGHT'S",
that allow the engine to load and unload are recommended.
AVOID PROLONGED CLIMBING MANEUVERS AT MAXIMUM THROTTLE.
2> After the first 45 minutes change to normal size prop
and fly an additional 45 minutes. Continue to run the engine
at a slightly rich four cycle setting and fly your normal
pattern.
3> After the above break-in period, run the engine at a
normal peak needle valve setting. This should be a little
on the rich side because engines run leaner in the air. 5%
- 15% nitro may be used.
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