Sorry guys, I should've been more specific. Yes, as Geo says, I've got HS6 carbs. I opened the float bowls and to my surprise they were filthy, with the lead bowl containing a fine sand of some sort. The valve was definitely stuck, and that carb was leaking all over that front area--from the bowl. Cleaned it all up, and now it's running great.
But, I just don't understand the mechanics here. What was happening? Here's a guess, and I suspect I'm wrong: the valve was stuck open and with the choke added to the problem. I had gas flowing into the bowl, out through the overflow, and with excessive fuel coming up through the jet and needle. Close?