XCell Spectra-G Model – Additional Operators Guide
Page 13 of 16
Copyright
12/5/2004
Miniature Aircraft USA
Use of the optional Hatori exhaust system will require the mixture settings to be made slightly
leaner, about 1/8 turn on each needle
Use of the optional air cleaner system will require the mixture settings to be made slightly
richer, about 1/8 turn on each needle.
4.4.2. Mixture Troubleshooting
General Observations
A good way to double-check the current mixture is to examine the spark plug. Operate the
model for about 5 minutes at hover or full power settings, then land, shut off the engine and
remove the spark plug.
Examine the porcelain nose on the plug for color and observe the following:
Black or Very Dark Brown
– mixture is very rich, which will result in excess deposits.
Recheck the carburetor needles and adjust to normal settings. Continued operation of
the motor with this mixture will result in excess piston deposits and can lead to a stuck
piston ring.
Brown or Light Brown
– mixture is correct. Make only minor needle adjustments to
resolve any vibration or tail-kick problems
Grey or White
- mixture is too lean. Continuing to operate at this mixture may result in
engine damage. Recheck the carburetor needles and adjust to normal settings.
4.4.3. Hover Settings
At hover, when the fuel mixture is correct, the model will be very smooth and the tail rotor will
sit nicely.
If adjustment is needed, the low speed needle will have the most influence on hover
performance. Using the normal settings will be very close to the correct mixture in most
climates (not high altitudes).
A slightly rich setting will tend to kick the tail rotor and a slightly lean setting will tend to make
the helicopter vibrate more. Adjust the low speed needle depending on the circumstances.
In addition, using the stock gear ratio provided with the Spectra-G model, at hover a Zenoah
motor will be very close to the low/high circuit transition on the carburetor.
If you find that the hover mixture is incorrect, (tail kicking or excess vibration) and making
small adjustments to the low speed needle has not resolved this, try making VERY small
adjustments to the high-speed needle to see if it will improve the engine smoothness at
hover. Make sure you know the original setting of the high-speed needle before making
adjustments and always use it as a basis for further adjustments. Otherwise the high-speed
setting can be unexpectedly changed significantly.
