Mini Ring Top Diagnosing Ink Flooding

[loganrah]

I have a lovely little vintage Wahl ring top gold filled lever filler I picked up from Greg Minuskin a while ago. Unfortunately I am having some trouble with the pen. In particular it floods and drips onto the page almost instantly when I start using it. I can sometimes get a line or two before it does so, but it almost invariably does so after that. 

At first I thought the issue was just hand heat causing air to expand and force ink out of the pen (which is more likely given its tiny size). However, I don't think this is the issue since holding the pen upright in my hand for several minutes to heat it up and equalise air pressure does not help the issue. 

So I suspect there is some other issue with the pen: perhaps the feed is not properly set or there is an air leak somewhere? 

What I would most like to know is how I should go about diagnosing the problem. I would prefer not to have to send it off for repair if it is easily fixable, but I will do so if I have to since in its current state it is basically unusable. 

The section seems to be quite tightly screwed in, I cannot remove it with reasonable hand force and I'm nervous about applying too much force with a vintage pen like this.