PZ Carbs have 2 jets. That is the main jet. The main jet does F-all for the idle. Changing it won't fix your idle.
The other jet, called a slow jet in Kehin speak, aka a pilot jet. This jet SLIGHTLY affects the idle, but mostly affects fueling from just off idle to 1/4 throttle. What size is this jet?
The actual thing that controls idle fueling is the idle mixture screw, not to be confused with the curb idle speed adjstument screw. One adjusts the static height of the throttle slide to change the idle RPM, the other is a tapered point that opens and closes a passage that draws fuel up from the bowl.
The idle mixture and idle speed screws are next to one another on the PZ19 carb. The mixture screw is angled down into the bowl closer to the rear of the carb (flange side). Since it controls fuel, turning it in leans it out, turning it out makes it richer. Too rich or lean will mess with the idle speed, so you will generally have to tweak the idle speed to keep it at idle speed.
The best idle mixture setting is one that allows for the highest and most stable idle.
Now, with ALL of that said. G2 reed setups are notorious for air leaks, and not wanting to idle is often a good sign of that.