Small Engine Troubleshooting Problems? Ask a Mechanic Now.
Welcome to JUST ANSWER small engines, let me try to help you !! I don't know it all, but maybe together we can get you a satisfactory answer!
I doubt the governor is causing the surge. Have you ran a cylinder test? Loosen the spark plug wires, and with engine idling, remove one wire at a time. Engine should continue to run. If it dies when wire is removed, the opposite cylinder is not firing! Missfiring/surging can be bad coil, bad spark plug or the valves need to be adjusted.
I see the question is still open, did you run the cylinder test? Result?