XCell Spectra-G Model – Additional Operators Guide
Page 15 of 16
Copyright
12/5/2004
Miniature Aircraft USA
5. Troubleshooting
The following questions represent some of the most common complaints our design team has
encountered in the support of gasoline-powered models.
a) When trying to get the motor up to hover speed, the motor bogs and won’t increase in
speed or may stop.
This almost always means the low speed needle is too lean. Open the low speed needle 1/8
th
turn and try again. Be careful though, the “initial recommended settings” are going to be very
close.
b) When trying to start the motor, it won’t start regardless of throttle setting
Assuming the motor has fuel, and the spark system is working, the low speed needle may be
too lean. Open the low speed needle 1/8
th
turn and try again. Be careful though, the “initial
recommended settings” are going to be very close.
Generally, if the motor won’t start it’s because the throttle trim has been set too low, or the
low-speed mixture setting is too lean
c) When the motor is first started for a flight, there is excess exhaust smoke and the
helicopter vibrates. After about a minute of hovering, the smoke stops and the
helicopter becomes smooth:
This is a normal behavior of these motors. It takes a minute or so to clear out oil residue in
the crankcase and for the engine to heat up to correct the working tolerances.
d) The motor was running fine and suddenly started to run erratically and won’t settle
down:
If this condition continues, mostly likely contaminants have gotten in the carburetor orifices.
We recommend using a pressurized air or other contact cleaner product to blow them out.
First note the exact position of the high and low speed needles then remove the needles and
blow them out using the pressurized method. This can be done with the carburetor on or off
the model. Then reinstall and adjust the needles to their original settings. If the orifices were
contaminated, the model should again run smoothly. If it does not, consider removing the
carburetor and checking its internal components for contaminants.
Carburetor repair is beyond the scope of this document, however Walbro offers a service
guide for their carburetors and repair kits are available for every Walbro carburetor.
e) After landing and returning to an idle, the engine is making a clattering sound but is
running normally:
This doesn’t necessarily mean that there is a problem, but it does mean the motor is VERY
HOT and the cylinder clearances have opened up. If the model has been flown very hard,
especially on a hot day you can expect this. The motor will cool off after a few minutes of
idling or steady hovering. It can also mean that the fuel mixture is too lean. If this continues,
examine the spark plug color as indicated elsewhere to make sure the fuel mixture is correct.
f) If I use a temperature measuring device, what temperatures are normal:
