I used to own an Aztek, and would have the same problem. When I thinned the paint more, It didn't seem to help....but I had to take apart the needle, like you said, and I cleaned it thoroughly, and still couldn't get it to work. Sometimes the tube inside of the paint cup gets clogged as well. The best thing I tried that got it working, was to take off the color cup and "inject" thinner directly into the AB. Once I got it to work, the next day it would do the same. Like you said a lot of tweaking. So, one night I got this brilliant idea to soak the whole AB in thinner to try and clean the clogs I couldn't see......and it ruined the trigger...after that I gave up!!!