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Carburetor 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-speed 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-speed
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.
CAUTION
: 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 230° F (88 to
110° C) range.
1 H
our
2 H
our
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 Needle
As you turn this clockwise (leaner),
less fuel enters the engine. Turning it
counterclockwise (richer) allows more
fuel to enter the engine.
High-Speed Needle
As you turn this clockwise (leaner),
less fuel enters the engine. Turning it
counterclockwise (richer) allows more
fuel to enter the engine.
Idle-Speed Adjustment
As you turn this clockwise, it increases
the carburetor opening at idle
and increases idle speed. Turning
it counterclockwise decreases the
opening and decreases idle speed.
Richer
Richer
Slower
Leaner
Leaner
Faster
