We modify engines in several ways fundamental to carburetor operation.

The most serious is the removal of the air filter and air box (plenum chamber). Two stroke engines are always pulsing air at the carburetor inlet. The prop wash and air flow across the carb inlet carries a large portion of the fuel charge away. The fuel charge is not carried away in chainsaw configuration. On a high humidity night shining car lights on an idling engine will allow one to see the halo (looks like a smoke ring) being forced out and back in the carb. It is an interesting phenomenon to watch. It is entirely possible that the engine cannot be richened enough to compensate for the loss of fuel charge. Making a very temporary air filter out of scrap foam might help lower the loss of fuel charge. Engines with cowls probably don’t loose as much charge. A velocity stack helped my engine, which is also open to the air stream. You might also consider that the airflow around the carb inlet is different on the ground than in the air. It might be necessary to set the carb adjustments for in air operation rather than best ground settings.

Is the engine going dead at low or high throttle?

Hope the information will be of some help.