Hallo Guys, I need your help.

I am the Agent for ASP Engines in Namibia, and I have sold many. I can not remember that I have ever had an engine that I could not tune or not diagnose a problem on.
I have however on Saturday come across an ASP 52a that is making problems that I can not find.

The engine is +- 2 years old, and is installed in an Acro 50 of my flying buddy. It has run like a Race horse for the past 2 years, including Saturday morning, when it suddenly stopped.
It would start, run up to full revs and perform flawlessly for about 2 minutes, and then suddenly without warning dead-stick. As in instantly stop running at different throttle settings.
We pulled the tank, thinking that the clunk had come off, it is still attached as usual. Then we removed the Dubro fueling valve (knowing that these sometime make trouble)bypassing it with a straight piece of tubing, still it will dead-stick. Then I removed the remote needle, and set it up as needle on Carb, still it would dead-stick. I then cleaned the carb by pumping fuel through it, still dead-stick after about 2 minutes of running. Then we replaced all tubing, with no luck.

Please help me as I can't think of anything else.

The Engine is fitted with a 12X4 APC prop turning 14000 RPM full on 5% Nitro, as it has always done. Transition is smooth and instant. Fuel is 18% Klotz 100 (50% castor 50% synth) 5% Nitro rest Methanol.
Plug is either OS No. 8 or ASP No. 4, this has also been changed during the whole exercise.

I'm at wits end with this one
Please help