torch still not happy :(

[crosby]

I had a problem with my torch, which I believe I posted before. I start out with a little acetylene, light the torch, and as per the manual, add a little oxygen using the mixing valve on the torch end. As soon as I add the slightest bit of oxygen, the thing pops and goes out. It was doing this about a month ago, so I took it apart, and sent the handle and the cutting attachment out to be rebuilt. It came back last week, and the oxygen trigger works great now, and it looks new! But, it's still doing it... Maybe I'm doing something wrong? On the handle, there is an F on side for the hose attachment, and an O on the other. One is reverse thread, so I don't see how I could screw that up. The F is for "fuel" right, the acetylene? And the O is for oxyen, right? I set it up with about 2 (pounds?) of acetylene, and 20 (pounds?) of oxygen, again, per the manual (roughly). I cleaned out the tip (brand new), and did the same thing three times. Any ideas? I am starting on a new frame, and really need to get this thing working. Thanks very much for any help you guys can provide.