You have some orifice plugged in your carb. By keeping the choke partially closed, this increases velocity in the carb, in turn forcing the fuel to pass thru its ports. Yank the carb, pull the bowl....on the bowl retaining "BOLT" there are two small passages. I found it best to either soak it in carb cleaner or at least pull one strand of wire from a wire brush and use that to "FLOSS" the opening. Pull out your mixture screw (be sure to put it back in its original position "TURNS" when you reinstall it) and check the tip....if it looks worn, bent...ect...replace it!
I suggest you pick up a rebuild kit for your carb before just trying to clean it. You said you have cleaned it a couple times with no luck.....sounds like you could also be in the need for some replacement of seats, screws...ect.
CLEAN,CLEAN and make sure everything stays CLEAN when you reassemble the carb.