Why oh why ? An 8N Update!

Running, All of a sudden it's worse than ever. Wouldn't start yesterday with out a 12V push. It's backfiring like mad. This is the engine that was starting so well in 8 deg. F temperatures. All I did was change the oil and put new copper core wires on it. The engine has stalled out twice on me while running. It restarted fairly well, But why did it stall? It's reminiscent of a gas tank problem I had before. I cleaned the tank throughly and it was fine until now. There just a tiny bit of rust in the sediment bowl. It doesn't look serious. Hydraulics, They seem to work OK. But I can feel the pump pulseing while I stand on the lift arms as it's going up. It also doesn't seem to be getting full travel. I brought it up to the max. Then I was able to lift the lift arms another six inches by hand This was at about 1000-1200 RPM. Is this correct? What's the best RPMs for operating the Lift arms?

The engine doesn't seem to really warm up. The radiator,head and manifold get hot, but the rest of it stays cool. I think I know the answer to this since there's no thermostat. Rich