Aztec Air Brush, success, finally

I purchased one of the Testors/Aztec air brush sets about 2 years ago and have been extremely unhappy with it. It would barely spray straight thinner and to get paint through it, you had to mix about 4 to 6 parts thinner with 1 part paint and then crank the air pressure up to about 20-25 psi. Needless to say, this much pressure behind really thin paint creates a "splatter gun" effect on the model. This was true when using the fine, medium, wide or extra wide tips.
I always considered the individual tips to be a unit that could not be disassembled and did the after use cleaning by spraying straight thinner through the gun until it came out clear. There was recently an article on the ARC (Aircraft Resource Center) forum that said that the Aztec tips can be taken apart and cleaned. I tried it and voila, problem solved.
There are five parts to each tip. 1) Outer case. 2) Inner case. 3) Spring. 4) Needle. 5)Gasket. Pull the inner case backwards out of the outer case, then pull the needle & spring out of the inner case. You have to pull fairly hard, but there are no hidden catches to be released for either part removal. Remove the spring from the needle. The spring is fairly small, but large enough to keep track of with a little effort. Clean all four parts, especially at the tips. Check the tip of the needle for burs by running your fingernail along it towards the tip. Do this all the way around the tip. You can also inspect it with a good magnifying glass. If you feel a small hook, very carefully rub the tip on a piece of fine sandpaper or wet stone and remove the bur.
Paint flows around the needle and through the inner case and then out the center of the tip. Air flows between the inner and outer cases and out through the tip drawing paint with it. Paint build up on the needle and in the inner hole of the tip was a small part of the problem.. The biggest part of the problem was the thin opening around the inner tip where it almost touches the inner edge of the hole in the tip of the outer case. Air was not getting past this point to suck paint through the center hole.
Take a pipe cleaner and thoroughly clean the inside of the outer case, especially at the front opening and just behind it. You may have to take the point of a #11 X-acto blade and carefully scrape the paint from the inner edge of the hole. There are raised channels inside this piece that match up with the four flanges on the outside of the inner case. When putting the inner case back into the outer case these channels & flanges must line up. If you hold the outer case in one place, the inner case can be rotated 90, 180, 270 or 360 degrees with no difference. Any one of the four positions will work for reassembly.
The inner case must also be cleaned of dried paint, both inside and outside, with particular attention to the tiny opening in the front end. There is a small, circular gasket around the outer case, just behind the knurled knob. This is essential for an airtight fit between the tip and the body of the air brush.
Blowing straight thinner through the brush after use cleans out most of the inner paint chamber, but it doesn't do much for the paint build up right at the tip.

Darwin, O.F.