Your engine is out of adjustment.

You need to get both needles set perfectly. Doing this require you to do some bouncing back and forth until you bring it all in. The high end is virtually a no brainer. The low is where problems are. A very simple test will tell you where your low end is at. While the engine is at an idle, pull the fuel line from the nipple or pich it off real good. Wait for the engine to quit.

If the rpms increas right before the engine quits, your low end is to rich, if the rpms hjust go down and quit, too lean. Try and find a spot where you get a very slight increase in rpm and I mean slight.