A couple of people have completely disassembled their compressors and they had no idea if the alignment was correct when it was reassembled. If the alignment is off, then the piston rubs in the cylinder and within about a half hour of running it, the piston will seize in the bore.

I have just figured out a simple way to check your alignment as you are putting it back together. Using the TOP cylinder, remove the backcheck assembly so there is a hole all the way through the cylinder. Slide the cylinder all the way into the airblock. Now put your eyeball up to the back check end of the cylinder and using it like a gun sight (you should all know how to do that ) line it up on the bearing in the rear support bracket. The rear support bracket is the one that supports the far end of the piston shaft. Twist the air block assembly left and right to get it just right. Then tighten down the air block screws nice and tight and you should be good to go!

If you notice that the bearing is very slightly low, that's ok, that's how this run came out. It does not affect performance.

Let me know if you use this technique.