10
Leaner
Richer
1 Hour
2 Hour
Carb Adjustments:
Make all carburetor adjustments
in one-hour increments. Imagine
the slot in the needle is the hour
hand on a clock. Adjust it as
though you were moving the
hour hand from one hour to the
next or previous one.
Low-Speed Adjustment
The low-speed adjustment affects the idle and slightly-off-
idle performance. The optimum setting allows the motor
to idle for at least 8−10 seconds. The model should then
accelerate with a slight amount of sluggishness and a
noticeable amount of smoke. The simplest way to check this
is to make sure the engine has been warmed up and let the
engine idle for 8−10 seconds. If the low-speed mixture is
so far off that the engine won’t stay running that long, turn
the idle stop screw clockwise, increasing the idle speed.
With the engine at idle, pinch and hold the fuel line near
the carburetor, cutting off the flow of fuel, and listen closely
to the engine rpm (speed). If the low-speed needle is set
correctly, the engine speed will increase only slightly and
then die. If the engine increases several hundred rpm before
stopping, the low-speed needle is too rich. Lean the mixture
by turning the needle clockwise one hour and trying again.
If the engine speed does not increase but simply dies, the
needle is too lean and needs to be richened up by turning the
needle counterclockwise one hour before trying again. After
you have optimized the low-speed setting, the engine will
probably be idling faster. You will have to adjust the idle stop
screw counterclockwise to slow the engine idle speed down.
The engine should accelerate at a constant pace without
hesitating.
High-Speed Adjustment
After initial acceleration, the engine should pull at a steady
rate while maintaining a two-stroke whine and a noticeable
trail of smoke. If the engine labors and is sluggish with
heavy smoke, the mixture is too rich and needs to be leaned
by turning the high-speed needle clockwise in one-hour
increments until it runs smoothly. If the engine isn’t smoking
or starts to die after acceleration, it is too lean and you must
richen the mixture by turning the needle counterclockwise.
Don’t be confused by the sound of the engine and the actual
performance. A leaner mixture will produce an exhaust
note with a higher pitch but this does not necessarily mean
improved performance, as the engine is on the verge of
overheating and may incur possible damage. Ideally you
want to run the engine so that it is on the slightly rich side
of optimum. This will give you the best combination of
speed and engine life.
NOTICE
: The engine is too lean and
overheating if it accelerates rapidly with a high-pitched
scream then seems to labor, stops smoking, or loses speed.
This can be caused by the terrain, atmospheric conditions, or
drastic altitude changes. To avoid permanent engine damage,
immediately
richen the mixture by turning the high-speed
needle counterclockwise at least “two hours” and be prepared
for further adjustments before running any more.
Note
: The
normal operating temperature as seen on your radio screen
should be in the 190 to 220° F (88 to 105° C) range.
About Glow Plugs
The glow plug is like the ignition system in your automobile.
The coiled element in the center of the plug glows red hot
when connected to a 1.5-volt battery (located in the igniter).
This is what ignites the fuel/air mixture when compressed
in the cylinder. After the engine fires, the heat generated by
the burning fuel keeps the element hot. Common reasons for
the engine not starting are the 1.5-volt battery being weak,
the glow plug being wet with fuel, or the element burned
out. Use a spare glow plug to check the igniter. If the igniter
makes the element glow, remove the plug from the engine to
check it in the same manner. A wet glow plug means there is
excess fuel in the engine. To eliminate this, put a rag over the
head and turn the engine over a few seconds using the pull
start. Reinstall the glow plug, making sure you have the brass
gasket on it. The engine should now start.
