I have here in my hand a Carb for the FA50.
It has a nipple at the bottom of the bowl with a nearby screw for draining the carb in prep for storage I assume.
This nipple is also connected to a vertical brass tube which is in the bowl and serves as a over flow vent.
The jet seat for the needle is close to the same height, off by about 2mm.
So all it should take is to lean out the needle by moving the clip up 2 or 3 notches.
I will give it a try and see what happens.
I have a carb/manifold that has been enlarge with a Dremmel grinder, (not by me) it leans out real bad at just over 20mph due the the small jet, I pull on the choke and get a burst of power.
The carb is clean.
I have a Chinese jet that was drilled with a #50 drill (if I remember correctly,) anyhow it's bigger than the stock jet and I will let you know what happens.