I like to buy old pens and put them back to work.
That usually involves new feed, new nib, sometimes a complete front unit, and new converter.
I rarely keep the sac since for me they never fill completely and you can't check the ink level before you run completely out of it.
I stay away from pistons since I don't know how to repair them.
This is more challenging than having "brand" pens where all the components are designed to work together flawlessly (although you will be surprised if I tell you stories...),
So, when doing the kind of things I do, it's a lottery to get a nib well coupled to a feeder, or to have the tines well aligned, or with enough separation, let alone all the problems with the converters. In some "peter pan" pens I buy a converter doesn't even fit so short cartridges have to be used instead.
Beyond the fun to solve all these problems, but not to drive myself nuts, and of course with the purpose of enjoying my back-to-life creatures, I've been focusing on the ink fluidity. I've found that, in most cases, a "wet" ink overcomes few flaws caused by not-perfect match between parts, and at the end makes things kind of more simple.
Since none of the inks is wet enough, I asked a chemist how to dilute, and the answer was with alcohol, same as we use for wounds. I've started with a couple of drops p/half full bottle, but I think that I can still push to 3 or 4. This is really trial and error, but it's just another way to get what we all want, an enjoyable ride with our little tools.
Last, I would like just to bring here that I've the most enjoyable writing ever with eyedropper pens.
I have 2 Stipulas, Passport and Paparazzi. Regardless the ink I feed them with, these little monsters start writing the moment I put the nib on the paper, and they never stop delivering a consistent, wet and endless fun.
I'm so tempted to try modern pens from India since most of them have eyedropper fill.
Have a great weekend everyone!