1977 dodge motorhome. The choke isn't opening all the way when I step on the gas so it stalls . What can I do?

An easy test would be to spray a little carb cleaner into the top of the carburator and see if it hits.

First thing to do is check the choke and make sure it works. When the engine is cold enough to need starting fluid, remove the air breather completely from the carb. get yourself positioned so you can see directly into the carb and open the throttle linkage all the way. You should see 2 things happen. One, the choke plate should close at least part way and 2, you should see a shot of gas going into the barrels. If you're not sure about the gas, hold the choke plate open and giver the linkage another shot.
If the choke plate didn't close, hold it closed with your fingers and try to start the truck. It should start, back off the choke plate a little and after a couple minutes it should be good to go.
If there was no gas, either it drains off or the fuel pump is getting weak. If the truck doesn't give you any trouble under moderate to hard acceleration, it's not likely the fuel pump. Trouble such as coughing or sputtering. These go away when you ease up on the throttle.
If it's the carb draining off then it is time for a rebuild. But, check around before you send it out. Call around and get a price for a total rebuild and then check online. It may be just as cheap or cheaper to buy new from someone like Summit Racing.

You found it,just replace fuel pump and fuel filter and make sure hose line from fuel tank is not crack

Could be a clogged fuel filter if the filter is between the pump and carb.

If you can spray carb cleaner in the carb then you have either a fuel supply problem or fuel delivery problem. Check your fuel pressure and make sure it is in spec. Then check the spray in the carb spray.

I'd check for a vacuum leak, the idle mixture. Also the check valve on the brake booster.

could be fuel filter clogged //fuel pump is going bad which you will need to have a pressure test done ...also is there a gas odor ? could be rusted lines could be air filter ....messing with the timing you should not move to much ...if you have brake /carb choke cleaner try spraying around the intake manifold to see if any change in performance such as lowering the rpm's which would mean a gasket leak are all the Vacuum lines good and not dry-rotted try bending them ans well as spraying with a squirt bottle of water on the plug wires to see if an Arc is present a bad plug wire ..these are a few areas in which i would consider 1st ..hope this helps you

Update? If the Motorhome has a carburetor, its pretty old and has a P30 chassis. Gm makes the truck, Honey makes the camper. Check the electric choke and make sure it has power to it when the engine is running, if not check all fuses. I dont have a diagram to see where the choke gets power from. Make sure the choke pull off is working, its a little vac can on the right side of the carb, if it leaks, it wont pull the choke flap open. Anyone that works on Quadrajet Carbs can fix it for you.

my guess would be to tighten up the choke a small bit

Most likely the accelerator pump in the carb is defective, take off the air cleaner lid, look down the carb while you quickly open the throttle, you should see a healthy spray of gas shot out.