You do have a fuel supply problem, not enough gas is being mixed with the air ( mixture too lean). This is why you have to use the choke (cut the air relative to fuel) to enrich the mixture and allow it to run.

I would first unscrew the drain plug at the bottom of carb and watch the gas flow out into a bucket. It should make a good flow and not stop, 3 gallons per hour rate at least. This is just a test to see if gas is getting into to the fuel bowl. If low flow, then the remove the line at the carburetor and check for a good flow from the line. That should be about 10 gallons per hour at this point. If not good here, then I think the sediment bowl is plugged,a light blow with compressed air may clear it (gas cap removed).

If flow is low out of the bowl you need to take carb apart and look at the inlet elbow, the needle and seat. Some thing is plugged up or needle is stuck closed. The float could be set wrong.  If you think it would be a good idea to blow compressed air into the carb inlet, don't , you could pressurize the bowl and crush the float. But the carb is probably

plugged up internally. If you have an adjustable main get, remove it and look for junk.

Another outlier cause could be intake manifold air leak.

An odd case, I have seen an engine run only with the choke on. The gas was contaminated with a high percentage of diesel fuel. It smelled like diesel, wasn't as "cold" to the touch like gas is, and a little oily by feel.

Yes, fuel cap.....OR

Was it running good with the old gas tank on it?  THEN I would suspect that the new tank has a piece of gunk in the outlet/inlet to the sediment bowl.

Was the new tank one that had the sealer put in it?

If it ran good before the tank swap, it HAS to be the outlet from the tank.