Dave, it sounds like it is indeed the governor, almost like it had been adjusted for near surge loading. If you or anyone you know that has a analog multimeter, it is an absolute must when adjusting the governor. It makes really short work of it too, as you can "see in real time" what it is doing when load is applied ad removed.
The easiest way to see if you genet governor is adjusted properly is watch you clock for accuracy, if it gains time or loses time it is running faster or slower than 60Hz, all 120v U.S. clocks are based on true 60Hz.