The engine is too lean. First, check that there isn't gummed fuel/oil blocking the carb jets. Use the pinch test to determine the right mixture.

With the engine at full throttle and leaned out to "smooth running", briefly pinch the fuel supply line:
1. If the engine sags and dies immediately, it's to lean.
2. If the engine picks up speed adn runs a while, it's too rich.
3. If the engnie picks up speed, then starts to sag and die, it's about right. Open the HS needle about 2 clicks from that and it should run well in the air. It the engine sags and/or dies in loops, open the HS needle a little more. Some engines unload like crazy in the air and must be set rich on the ground.

There's only one proper way to set a ST low end needle:
1. Install a short piece of fuel tube on the carb inlet nipple.
2. With the throttle barrel at idle position (engine NOT running), hold the carb throat to your ear and blow into the fuel tube.
3. Gradually open the idle needle until you can JUST hear air blowing through the carb. It'll be within 1/8 turn either way of being right.

Dr.1