I have a pair of later SUs, the ones with the large metal thumb screw mixture nut rather than the knurled one. I have tried everything to get the nozzles out, but they are stuck tight! I've detached everything from the nozzles and tried a little penetrating oil, but they won't even turn. In fact, the only way they raise and lower is by loosening or tightening the mixture nut. I did a minor rebuild on a different set of carbs, and the nozzles slipped right out once everything was disconnected.

Any ideas what I'm doing wrong???