If you're referring to the slow jet emulsion tube or "jet set"....item 25 in the link below:
YES! The tube is supposed to be "open" all the way down. BUT....DO NOT TRY TO FORCE A CLEANER FILE THROUGH IT.!
Because, what you're encountering is the actual reduced diameter of the jet itself.
Any attempt at "gouging" out the jet with a tool or wire usually only results in damage to the jet.
If you can't clear that orifice with carb spray. I highly recommend that you replace the tube with a new one.
That tube and it's little oring have a major role in how the carburetors function. If you can't get it totally clear with carb spray but try to reuse it, you will likely find that you'll soon be pulling the carbs off again real soon.
I KNOW....not what you want to hear but that tube has bitten most of us that have worked on these.
I used to do these carbs weekly and used an optiscope with 40× lens to clean that tube because the jet is so hard to look through. BUT...I finally realized that they just weren't worth the trouble. I decided to just stock new ones and swap em out to make my life easier and the work go quicker. Your choice though.
In addition to the jet and all holes needing to be perfectly clear, that tube also has a tendency to crack and split up the side. So watch out for that too.