I've had a lot of questions from other forums about my Gas engines with onboard starters. I'll start this string to see if there is any interest in the subject.

The photos below show a small starter installed on my Robin conversion engine and one that I am working on on a Toro comversion engine. I have a G62 with starter on a big 1/3sacle Citabria and 1/3scale Spacewalker with an old Quadra 42 with another starter design.

The starters are powered by an electric car motor that drives a series of gears to a main drive gear with a torrington clutch bearing (same as a spring starter bearing). Everything is controled by one channel on a slider switch on your transmitter. One end is the kill switch and the other is the starter engage.
The center is run. Most of the parts are off the shelf with only minor metal fabrication required. The main thing is you have to have a rear shaft to drive for the starter to drive.