Actually, the tank looked nice and had almost no rust inside, so I already wondered if I should try to clean it. Glad I did it, because after emptying the tank and removing it, something went "clank clank" inside: some idiot had sunk a screw and a nut in it! These were completely rusted, so that was the explanation for the dirt in the carburetor.
I figured out the easiest way of removing the rust from the tank was to fill some highly concentrated multi-purpose kitchen cleaner inside (sort of soap that contains loads of citric acid), and fill up with water to the brim. The rust bubbled up and could easily get removed by pouring some more water in every now and then to flush the floating rust foam away. Eventually, no more rust came up even after shaking the filled tank. Tried then a 1:4 mixture of DanKlorix:water, but there was no visual effect. Filled in half a liter of spirit, shook well and then emptied, to get rid of remaining water inside. Did about the same with both fuel filters (someone had already equipped my Camino with an extra one just as shown above!), fuel hoses and tap. After initial starting problems and readjustment of the gas/air screw (it seems to have at least some effect now), it runs well! I'm glad.
In the meantime I got myself a "small upgrade", a Honda Rebel 125, but I still enjoy riding the Camino. And my son will soon too
