Greetings Doug, thanks for the welcome.
The youtube video shows the genset operating at 37Hz output. The belt ratio is 1:1 and so the engine would have been running at 1110 rpm.
youtube AVA1 video linkThe video was taken when I was making some adjustments to the governor, also the alternator was on load with both an electric fire and heavily charging the starter battery.
I have myself come to the conclusion that I may need to obtain a new weaker speeder spring but I have no idea about how to make one, the engine seems to regulate better at 1200 rpm than at 1500 rpm as I want it to.
Another possibility would be to fit a larger belt pulley onto the crankshaft and run the engine at a slower speed. I have made some tests at 1200 rpm but although the regulation is better it still isn't very good.
I expect that the only satisfactory solution will be to fit an electronic governor, this will also allow automatic stopping of the engine by removing the fuel supply when needed.
I have looked at the web pages you linked to but I haven't yet spotted the injector pump on the engine there.
Best regards, David.