Bwana Kiko , In your pipes the aluminum piece, screw side is supposed to stay in the stummel and the mouth piece should be able to slide off of the larger smooth aluminum side. The problem, as you know, is that corrosion or gunk gets between the aluminum and and vulcanite stem. That stops you from being able to remove the stem. You need to make sure you remove off the smooth aluminum side by turning the mouth piece clockwise so it keeps the screwed in section secure in the stummel.
