WC only runs right with choke partially on

Open up the main jet on carb one full turn or more.

Is gas going to carb? Maybe screen plugged.

Intake manifold may have a leak.

Steve in NJ wrote: Sounds to me like a lean condition. Intake vacuum leak. Pinhole or crack somewhere possibly. Engine may need a fatter mix under load if idle and off-idle are good at the Carburetor and under load is a problem. Fuel delivery problem to Carb... HTH Steve@B&B

I'm currently having the same problem with a wd45.  Also had the head redone.  Have 2 situations...carb and lower manifold ice up, so I put a thermostat in, idle for about 5 minutes until manifold heats up and ice goes away --- but then will still only run with choke half closed.  I've gone thru the usual, including 3 different carbs and 2 different manifolds; drained tank, pulled bowl assembly, new fuel line....still stumped.  I've let it sit for about a month now, will have to get back into it soon.

So dad was using the wc and it quit running one day.  So we  put a new coil, condenser, filed the points, new rotor , cap, plugs and  plug wires .   That got it running again but still had to have choke on a little but maybe a little better.  tried to adjust carb and no adjustment did anything to how it ran other than when main jet was screwed all the way into seat.  Took carb apart and cleaned every jet with wire and blew everything out.  Put it back together and ran almost perfect without the choke on.  But when you put it under a load it starts to stall a little.  But no matter what you do with the top adjustment for the air mixture it doesn't do anything.  You can take it all the way out and doesn't do anything.  Bottom screw only changes engine when it is screwed all the way into the seat.  But no matter how far you screw it out it never runs rich.  Also put new needle valve and seat in.  Plus new float.  Any ideas???  One place told me to toss the carb and put one off a wd on it.  I think the one on it now is a Zenith 7078.  Also sprayed starting fluid on intake and carb and it had no change in sound.  Has me stumped.

Do you happen to have a filter between the tank and carb.?

If your not getting any change with adjusting the enrichment jet, there's a blockage or a problem (crack) somewhere deep in that Carburetor. The upper air/fuel mix screw is basically just for idle. The lower adjusting jet is for enrichment under load. (working)  If you crank that enrichment screw out at full throttle you should start to see a tinge of black smoke from the stack. After reinstalling your Carburetor and seeing how the engine ran much better with almost no choke, showed your cleaning method helped. These Carburetors can really get some dirt and debris jammed in their enrichment and idle circuits. Being I rebuild a lot of these Carburetors, I can't stress enough about making sure the fuel tanks are spotless, along with the fuel delivery systems. It doesn't take much for these Carbs to get messed up. The 7078 especially, being it was a dual fuel Carburetor to start off with. Distillate fuel wasn't the cleanest....
Steve@B&B