Not something I would do. Why?
Early in my career I was working on a Rochester Quadrajet on a V-8 Chevrolet Chevelle. I had rebuilt the carburetor but was having problems and I decided to save myself some time and take the top off of the carburetor and work on it while still on the car. Things worked OK until I dropped the check ball down the carburetor, which then rolled down the carburetor and into the intake. I wasn’t completely sure it actually ended up in the engine so I started the car. Ping! Ping! Ping!, I could hear the little check ball bouncing around. Check balls are stainless steal so they are pretty hard. Now what? Well, I had to remove the intake manifold and the head on one side of the engine. There the little devil was, embedded into one of the pistons.
I get the question asked about working on the carburetor while still on the car every so often and this story comes to mind every time.That was an expensive lesson I’ll never forget.
Bottom line. Always take the carburetor off of the car before taking it apart and when do other work around the carburetor, put a rag over the throat so nothing can drop inside.