ORIGINAL: BaldEagel
Forgett all the diagnosise of the position of the wires to the throttle servo, you are using a system that does not accept RF interference, it can only be direct electrical spikes through the wiring or a bad servo. My guess is a servo gone down, the amount of vibration comming throgh the operating rod too the servo and the heat etc, is going to cause a throttle and or choke servo to go occasionally. I tend to use an Analoge coreless for both and change them at the end of each season.
Mike
A coreless servo is a bad choice for a throttle servo. The delicate armeture is very sensitive to vibration.
Chose a servo with dual ball bearings and a three pole motor. Nylon gears are probably best as they would tolerate vibration better than metal.
Take a look at the digital sport servo. It would probably give you the best operation and reliability.
As for the interference go to 2.4 ghz and forget it.