OK, thanks for your opinions guys. Yes, I do understand that magneto or electronic ignition gasoline motors will produce more EMI than a glow motor (which has zero ignition).

I was surprised by the consensus against mini servos, even ones with reasonable ratings like the HS-81. Even ignoring EMI, it's rather surprising to hear that people think the servos won't last in what's obviously a low torque situation. Sure the vibration is a major concern but I've seen similar servos used on big Saito four strokes that had hideous vibrations.

The suggestion to use nyrod is good but it's a physical impossibility on my engine. For starters the Walbro is mounted up on the cylinder in a Homelite which makes routing a little trickier. There is also the issue of throttle arm being at an angle and requiring a push in an upwards direction.

I will reconsider using a standard servo and look at using a bellcrank setup (painful as that will be).