1980s OMAS flow issues

[guyy]

I’ve had the same problem with both of my 1980s OMAS 557/f pens: ink doesn’t flow consistently to the nib even with a full load of the most benign of inks (e.g., Waterman Whatever They Call It Now Blue). I have to crank the piston down to get some ink in the feed. The pen will write ok for a while, then it will run dry again and i’ll have to repeat the process. I’ve tried repeated cleanings without improvement. I barely use the pens because they’re such a bother.

I’m looking for suggestions on how to improve the flow. My conjecture is that the wedge shaped channel in the feed isn’t sufficient to get air up and ink down.