XCell Spectra-G Model – Additional Operators Guide
Page 12 of 16
Copyright
12/5/2004
Miniature Aircraft USA
4.3. Operation During Break-In
Always follow the instructions from the engine manufacturer concerning any special operating
procedures for break-in.
In general, the model can be operated normally although it is suggested that the rotor head
speed be limited to 1650RPM for the first 2-3 gallons of fuel.
The break-in period for the Zenoah G23/G231/G26 engines is about 5 gallons of fuel. The
engine will gradually break-in and will develop more power and run smoother during that
period. During this period, you will gradually be able to lean the carburetor mixture settings to
those considered “normal”.
4.4. Normal Operation
4.4.1.
Normal Carburetor Settings
The exact carburetor settings will vary slightly according to temperature, humidity, altitude
and rotor blade size, however between 1 and 1-1/2 turns on each needle will be correct in
general regardless of carburetor.
Adjust the low-end needle for smooth operation at up to ½ throttle. The low-end needle
controls the mixture from throttle closed to ½ throttle with no interaction from the high-end
needle (in fact you can close it and the motor will run fine up until the transition point). There
is a small portion of throttle travel just above ½ where the setting of the low and high speed
needles transition. Above that point, the high-speed needle will significantly affect the
mixture.
The low speed needle is very sensitive. Make adjustments in very small increments (1/64 turn
at a time). Do not make large adjustments to the low speed needle! The high-speed needle is
less sensitive and can be adjusted in 1/16 turn increments.
The correct low speed setting is when the model will hover cleanly. If the engine is too rich it
will not clean out at hover, but instead tend to “four stroke”. This will be very evident, as the
tail rotor will tend to “kick” in a hover.
If the setting is too lean, the engine will tend to bog (its really starving for fuel) when the
throttle is advanced. It will be difficult to get the motor to run fast enough to hover or it will quit
running.
The correct high-speed setting allows the engine to operate cleanly above ¾ throttle.
After break-in the following Needle Settings are typical for these carburetor models installed
on a Zenoah G231 engine using the standard gear ratio of the XCell Gas model:
4.4.1.1. Walbro WT-677
Low Speed:
1-2/3 turns open from full closed
High Speed:
1 turns open from full closed
4.4.1.2. Walbro WT-643
Low Speed:
1-1/2 turns open from full closed
High Speed:
1-3/8 turns open from full closed
