Your experience pretty well matches mine. A student brought one of those Xtra Easy trainers with the MDS .40 on it. Deadstick deadstick deadstick, usually within 30 seconds of taking to the air.

I listened carefully, and could hear the engine slowing down gradually, a sure sign of too much fuel. Two or three guys tried tweaking the high end repeatedly, only to have the engine deadstick. They ignored me when I suggested the idle mixture was way too rich, but another instructor said the same thing, they listened, and the engine ran much better.