Bring it to the lowest idle that it will maintain and pinch the fuel line.

The engine should run for a few seconds, during which time it should increase in RPM. Then it will die.

If it dies right away, the low end is too lean. If it runs for more than a few seconds, it is too rich.

The LA series has an air-bleed adjustment on the low end, so if it is lean, close the adjustment screw. If it is rich, open the adjustment screw. This regulates the air coming in that tiny hole in front of the venturi - also check that the hole is not clogged.