Many years ago I had the slide stuck in an Amal carb. The bike had been sitting for many years. Removed the whole assembly and put it in a pot of warm water. The heat allowed for the slide to be removed. With older Amals the slides and carb body are made from the same die cast zinc pot metal and that isn't good. It is best that the slide and body are made from different metals such as zinc for the body and brass for the slide. They won't wear to each other which is another problem.