I've the same issue on a 990 carb in the 5ive.
If I set the carb to factory setting and have the idle screw just touching I'd never start it.
If I was to lean out any more on the low end is kill the engine, well I think I would? As it's sitting at 1 turn from closed at the mo.
If you've another carb ie choked style I'd give that a go maybe and see.