WHAT DOES „RICH“ AND „LEAN“ MIXTURE MEAN?
Adjusting the carburetor is one of the most critical things when driving fuel powered RC cars. It refers to the mixing
ratio as „rich“ when much fuel in proportion of air gets in the carburetor, and as a „lean“ with low fuel in comparison
with air. The fuel portion is set with the high-speed and low-speed adjustment screws. The low-speed screw is located
on the front carburetor linkage side. The high-speed needle stands bolt upright on the back of carburator. If you rotate
the screws in clockwise direction, the mixture is getting lean and vice versa. A pronounced „rich“ mixture shows slowly
acceleration and less performance with thick smoke from the exhaust. In „lean“ mixture the engine can „swallow“ before
then rev up suddenly, or maybe, after a short initial acceleration slowdown in the performance. A lean mixture leads to
undesirably high engine temperature and reduces the lubrication of the engine parts inside, leading to excessive wear
and damage.
It is always advisable to run the engine slightly rich and never lean to avoid overheating and pos-
sible damage.
MOTOR TUNING
If the engine is run-in, you can set it to maximum performance. It is important that you carefully
watch the engine temperature, overheating cause serious damage and excessive wear. Make any
changes to the carburetor screws in the 1-hour increments (see fi gure).
Caution: Warm up your engine before making adjustments on the carburator set-screws
(min. 70 - 80°C)!
Proceed as follows:
Turn the high-speed needle adjusting screw to approx. 1/8 revolution leaner. Then run the car approx. 1 - 2 minu-
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tes, check the engine temperature (not higher than approx. 80° C) and turn the engine again approx. 1/8 revolution
leaner.
Pay attention not to run the tank completely empty, because the engine, before it stops, runs too lean and therefore
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suddenly revs up. In addition, that can lead to precocious engine wear and it is dangerous because the vehicle will
get suddenly faster and can get out of control.
The nearer you come to the optimum settings of the engine, the smaller the steps of turning the screw must become,
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at the best only „1-hour-steps “, see fi g. above.
Repeat the procedure until the engine has a good performance and its temperature lies in the green range (max.
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120° C). Perhaps you must unscrew the idle adjusting screw again a little, if the engine runs too high in the idle.
Next the lower speed range is adjusted with the help of the low-speed needle adjusting screw. Proceed here si-
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milar as for adjusting the high-speed, until the engine does not overheat also here and accelerates well. Because
the high-speed and low-speed adjusting screw are connected in some way, you must set the high-speed adjusting
screw maybe a bit richer when the low-speed range is adjusted correct, so that the engine do not run too hot and/
or runs too lean on full speed.
Repeat these steps until the engine runs perfect over the complete speed range.
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LOW SPEED NEEDLE ADJUSTMENT
The low-speed setting affects the performance of idle and slightly higher. The optimum setting is when the engine runs
for at least 8-10 seconds in idle, then, the vehicle then should accelerate with a slight amount of sluggishness and a
noticeable amount of smoke. The simplest way to check this, after the engine is warmed up, let the engine run in idle for
about 8-10 seconds. If the idle mixture is adjusted so that the engine is not running so long, turn the idle screw clockwise
to increase the idle speed. While the engine rotates in idle, pinch now the fuel line close to the carburetor to interrupt the
fuel supply, and listen to the engine speed. If the low-speed needle is set properly, the engine speed will increase only
slightly, and then die. If the speed before dieing increases several hundred revolutions and remains there, the low-speed
is too rich. If the engine speed not accelerates, but rather simply dies immediately, the setting is too lean and must be
set by the screw an hour in direction “rich”. If the low-speed needle is optimally set, the engine is idling probably in a little
bit higher RPM. Then you have to adjust the idle set-screw counterclockwise to reduce the idle speed of the engine. The
engine must rev up with constant acceleration and run without breaks or delays.
GM-Racing 90171.RTR Flash 3.0 Race Nitro 4WD Buggy 16
Содержание Flash 3.0 Nitro
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