Like T-Bucket said, it sounds like you have a problem with the high idle cam and/or adjustment. Do you know how to adjust it? Do you know where it is? It is really easy to adjust once you figure out where it is and how it works.
Last engine I dry started the high idle cam was 'stuck' from the carb sitting around for a couple of months after being rebuilt. When it was started it wouldn't idle down as the choke opened. I shut it off, opened the throttle wide open and tapped on the high idle cam, literally a light tap, and it freed up. Problem over.