So, I recently bought a Parker 51 from the flea market. It was in a pretty sorry state. I did a complete restoration.After removing the hood, cleaning the feed, collector, breather tube and so on, I went on and replaced the filler unit with a new one. Then I polished the exterior of the pen using a buffer and then some micro-gloss. All good so far. I started to write with the pen. It produced a very wet line and the writing experience was super smooth. Then this happened. After a few sentences the pen started to become very dry and after a bit more the ink flow completely stopped. I waited a bit and then it begun to write again. This was an endless loop.
The first thought that crossed my mind was that I am dealing with a not so clean collector. I cleaned it. Still no luck. I tried a new collector. Same...the pen run dry. I tried a new nib, a new hood, a new feed nothing. And then I thought about the way that ink is delivered into the collector. THE BREATHER TUBE. It has a hole on top, which allows the user to fill ink without, removing it every time the filler is pressed. However there was no hole on the bottom (or at least mine didn't), to allow any ink to escape from the barrel and go back to the feed/collector. (In contrast with the aerometric breather tube that has one, for this purpose). This had to be it, there is no other logical explanation, I said to myself.
So I picked up a dental hook, heated the end of the hook with a torch , and then opened a tiny hole just above the bottom of the breather tube.
(It had to be smaller than the one on top, because if it wasn't then it would defeat the purpose of having a breather tube in the first place, which is to have more ink going in, than going out.)
I then reassembled the pen and begun to write.
That did the trick, the ink flow is now super consistent and pretty wet (Note that the size of the hole that is opened, determines the wetness of the pen. The smaller, the dryer). For anyone who will ask, no there are no leaks, no ink blots, just a very satisfying wet line.