I bought the same float as ebay #130814681139 for my 1928 D to replace the cork one -except mine came with a tiny Phillips head screw - grrr -very hard to tighten -- when I installed the float on the rod, there is a short slot in the choke rod that you can adjust the cork in towards the float or away.... When I first tightened the float, I checked range of travel. I lifted the choke all the way and blew into the fuel supply elbow -air was slipping by the needle- I realized that the float was contacting the side of the bowl and stopping the float from raising all the way to shut off the gas flow. adjusted the float towards the needle as far as it would go and now the air was shut off.
After running for a couple of hours -I went to start the tractor, turned on the new three way valve, and gas poured out the top of the load nozzle bore.
I removed the bowl from the carb-which you can do with the DLTX 3 and a 1928 D -without removing the carb ---
I connected the supply elbow to my little starting tank, held a rag under the bottom of bowl and turned on the gas -the float did not rise-I removed the float from the rod -the joint between top and bottom of the float had split from minimal solder used -I re-soldered the joint, reinstalled everything making sure the float was pushed back - and the carb worked good ---