You never said if you tried new fuel. In the past two years, I have seen fuel go "bad". Its very frustrating until you recognize it. My nephew had this problem at the beginning of the season. The fuel he had stored all winter (not an airtight bottle) had probably absorbed too much water. He would fuel the plane, get the engine running, take off, and then a few minutes into the flight - deadstick. He just borrowed a tank of fuel from another flier, and the plane flew beautifully for the entire tank. Its easy to rule out.

I personally don't like the four stroke glow plugs on a two stroke engine. The plugs run so hot that the engine timing ends up early, and it just ends up wasting fuel.

There's nothing to go wrong with the LA carburetors. If the fuel passages are open, they're pretty much bullet proof. But it doesn't take much to block a fuel passage. A small piece of plastic from the tank (the size of the head of a needle is huge) is often all it takes.

The airbleed screw should start with the air bleed hole 1/2 blocked, and then adjust from there. If the end of the airbleed screw has been damaged, that can screw things up (sorry about the pun) as well. A small piece of dirt or grass in the hole will drive you crazy chasing the tuning.

Finally, take the tank out and inspect the internal lines very closely. A small crack or hole in the fuel line will allow air to be drawn in, cause the engine to go lean, and - deadstick. When you put the smaller tank in, did you replace the lines?

Brad