Thanks for the comments. Cleaning the nibs and feed systems isn't really the problem. That's generally easy as the ink is water-soluble. The thing is some of the feed systems just don't work that well to begin with and I can't see that they ever could have. It is a design problem, and as I said the design variations are numerous. The most consistently bad feeds I've found have been the ones in the hooded Sheaffer's pens. The interesting thing is that you can not take them apart, so there is no hope of correcting them. They're molded in place. I've yet to see one which worked very well.
Jon