Small engine experts?

I have a Ryobi “weedwhacker” model 790r with a 31cc engine. There is a trigger type throttle and a 3 position choke lever. You set the choke in position “A” and pull until the engine “pops”. Move to position “B” and pull until the engine starts. Let it warm a bit in B. Switch to position “C” and have at it. PROBLEM: when I pull the trigger throttle the engine dies. My impression is that it isn’t getting any air and I am killing it by giving it more gas, since when it dies the exhaust smells too much like gas. The air filter is clean, and I get the same results even with the air filter off. I am not a small engine expert. Ideas?

First place to look is your plug.

It might well be fouled up if the oil feed is too rich, or the plug might just be tired, or the spark gap too great.

After that you would look at the HT lead and then the timing which might be out a little.

I agree that a new plug is not a bad idea. Cheap easy and fixes a lot of bad things.
I think there is something that you are not clear on.

The throttle adds air to the engine. The carb adds gas based on air flow.
I would suggest that you change the plug, if that does not fix it then look at the carb. I had a similar problem with my lawn mower and I found a piece of crud inside the carb. Removed the crud, and it runs great.

Or… the throttle cable is improperly adjusted, which would cause the throttle blade to open, and then close again. If it’s like mine, take out the air filter, look inside the carb while pressing the throttle back and forth. Check to see if the throttle is wide open when the trigger is fully depressed, the throttle blade should be open all the way. (do this with the engine off of course)

I had the exact same problem. The vibration had loosened the bolts that held the carborateur onto the manifold. Whenever I revved up, it would lose vacuum and die. On mine, I used an allen wrench to tighten things up and everything worked fine. Now, I just automatically tighten the bolts before I use it. You could also get some loc-tite at any autoparts or hardware store and that would fix it.

Sounds like carburator problems. Or at least fuel problems.
Check to see if the choke is working properly.
Check the fuel filter.
Since its this late in the year can we assume it has at least worked correctly this year?