Hello everybody,
Just a few days ago I received a new Jinhao X450 from a Chinese seller. Soon after I started writing, the pen leaked. Ink came dropping from the nib until the converter was empty, and my paper was a mess. This was the very first problem I ever had with any Chinese pen. After I rinsed and flushed the pen, I pulled out the nib together with the feed, and while doing so I realized that the feed was somewhat loose. So, I cleaned everything under water, dried it and assembled the pen. I filled the converter with ink again, and everything worked as it's supposed to.
My conclusion: the feed had either loosened, or wasn't assembled correctly. A small cause for a big mess!

So, if someone has a similar problem, this may be the answer.

I have a couple of Huashilai 3000s that would occasionally drop a big drop of ink on the paper, of course without warning. After reading around on the FPN, I suspected that the converters weren't seated properly, and were letting air in, and ink out. Reseating both converters fixed the problem.

One of the nice things about really cheap Chinese pens is that you can pull them apart and fiddle with the bits without feeling anxious. Of course learning something about fountain pens at the same time.

I spoke too soon. The leaking problem occurred again. Now I suspected the converter. So I exchanged the converter of the X450 with the one of my X750, expecting the X750 to leak now. It didn't. So far, after writing about three pages with each of the pens, none of them leaks. Now I'm pretty much clueless as to what caused the leakage in the beginning. I also found that the converter that came with the Jinhaos differs a little from the "universal standard" converter. The opening is just a tad larger. Any idea where to buy converters for Jinhaos (at a reasonable price!)?