Suburban, there’s a good reason that optical kill switch caused the problem. Take a look at it. One set of wires goes to the ignition battery. Another set goes to the ignition module. Those two sets of wires could be contaminated with radio frequency components that are in the 2.4 Gigahertz range or some other range. Those wires are very long and can act like a perfect antenna transmitting the RF just like the antenna on your transmitter. The third set of wires goes right in to your receiver. They would conduct any contamination in to your receiver. You have two things going against you, radiation and conduction. The Smart-Fly kill switch has a transmitter and receiver that are separated by a lengthy optic fiber line. This will give you the isolation all the radio manufacturers recommend. Always make sure that all your ignition components and radio components are separated from each other as far as possible and I mean always. Thanks for posting the solution. It’s a good thing you found it. By the way, there is nothing wrong with the carburetor cut off. It was satisfactory for years and still is. Dan.