peak setting followed by richening
to cool. Do this about 10 times
throughout the course of this tank
of fuel.
5. Leaving the high-speed needle in
a peaked condition, check your
throttle response, going from
low to high and back, gradually
lengthening the duration of high
rpm. Continue the break-in process
until you can get a stable high rpm
for at least one minute. At this point
the ground break-in is complete.
Carburetor
Adjustments
Low-speed
needle
High-speed
needle
Notice: Before adjustment make sure
the low-speed needle is set at the target
position. In particular make sure this is
done after doing the break-in process.
It is also preferable to start with the
main (high-speed) needle ½ turn open
from the target position. In principal
the carburetor should be adjusted by
first achieving peak rpm with the main
(high-speed) needle valve and then
adjusting the low-speed needle valve.
(Until the high-speed needle setting
is fixed low-speed adjustment will be
difficult and not stable.)
1. Fill the fuel tank and then start the
engine as previously described.
After the engine starts allow it to
warm up for 20 seconds and then
fully open the throttle.
2. Utilizing a tachometer, adjust the
main (high-speed) needle valve to
peak rpm carefully. Note as you
lean the motor the drop off in rpm,
richen back to the peak rpm from
that position.
CAUTION: Over-closing
(leaning) the main needle valve can
be dangerous, causing pre-ignition,
knocking and possibly loosening the
propeller. If you hear these symptoms,
immediately richen the needle valve.
3. Next close the throttle until the
engine idles reliably at about 1700
rpm. Careful coordination between
the idle (low-speed) needle and the
throttle position is needed to achieve
this.
4. After you have a reliable idle now
check for a good slow transition
from low to high. If the engine
C A R B U R E T O R A D J U S T M E N T S
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