The symptom: The stove started to burn ineffectively, progressively demanding very high pressure inside the fuel chamber just to achieve a low burning. Searching the web, i studied pages like this: Optimus 324 Rider ridden hard trying to understand where the problem might be. The problem seems to be inside this tube, shown in the image... I was surprised to realize that, blowing with the mouth the one end of the tube, air does not pass to the other side freely. I do not understand, what could be the reason of this clog. Should not this tube be empty? Should not the fuel pass freely inside the tube over the flame to be preheated? What might be inside the tube? It seems to be something very hard and of a metallic nature. Any help to understand this puzzle will be much appreciated. Not being a mechanic of any kind, i just gave up!