Got my G out of the shed yesterday for a spring warm up. After maybe 30 minutes of running down the road full throttle, when starting up a slight incline, putting the engine under a little load, it began to lose power and surge. When choked it got worse momentarily, but then straightened up for a while. As I recall, it was doing the same thing last fall and I never got to the root of the problem. It has new gasoline, good fuel flow, no water in fuel. Carb had been thoroughly cleaned (tag wire through all passages, soaked in cleaner, spray cleaner used too and blown out. Float set to spec. Any ideas?