Still sounds like the disc is opening the wrong way...It should open toward the 3 small holes in the venturi..
I just ran 2 conversions this afternoon..If the needles are open too far the engine will cut off just like you describe...Most G26s run with the needles open at 1 1/2 or less...The carb is so big it's touchy...I always start at 2 turns and set the high first...Then set the idle speed for about 2000 rpm...slowly close the low needle, the engine will speed up...Re set the speed to 2000 and lean the low needle some more..Do this until it no longer picks up speed and the idle is 1800-2000..Now when you open the throttle it will die..Open the low needle a little at a time until you can get a good transition, then re set the high..It should be good to go...The low needle needs to be a little rich for good transition, so the idle speed will be controlled by the low needle as well as the speed needle..Hard to put down in writing, it's something you have to mess with to get it right...