About 3 years ago I bought a Zippo Blu² lighter (which, apparently, has not only been discontinued in 2016, it has been completely eradicated from the Zippo website). I liked it because it was a flint-based lighter (I had heard piezoelectric ignitors would not work at extremely cold temperatures), because it was butane (I don't smoke so liquid-fuel Zippo lighters would evaporate before I could use them), and because it was a genuine Zippo (thus, likely to work correctly all the time and for a long time.) It generally worked just fine—I don't use it much at all, though, so any frequent user will likely have encountered these problems already. I refilled it numerous times over the years and, in general, it worked great. (I did read online a recommendation to completely empty the lighter of butane before refilling by depressing the fill-valve until the "tank" is empty. I'm not sure if that's necessary, though.)
Recently, though, I started getting a really anemic flame. It was enough to make fire, but nothing like the torch-like behavior I was used to. It was such a weak flame that you could blow it out—so much for "windproof"!
I checked online to see if this was a problem and if there was a solution. I found Mark Shell's video on fixing his Zippo Blu which is basically exactly what I'm about to outline here, so if you'd prefer to watch a video, then Mr. Shell's is as good as any.
Indeed, flint and debris filled the vent holes around the lighter burner—almost certainly the cause of the small flame:
I used a straight pin like Mr. Shell and poked the vents clear:
As you can see, the vent holes are now rather clear by comparison:
Unlike normal people, I don't have a spray-air can around so I resorted to an air compressor blower to get rid of the rest of the loose dust and dirt:
Finally the results: a nice strong flame again: