4 stroke carburetors don't have the same pilot circuit as 2 stroke carburetors. 2 strokes have a pilot jet which is immersed in fuel in the float bowl and then a "T" built into the side of the carb where one end dumps downstream of the slide (towards the engine) and the other ends in a vacuum adjustment needle, "air needle", "pilot needle", or simply "that screw thingy". The idea is to adjust the amount of vacuum in the "T" which will change how much fuel gets drawn through the pilot jet. It works, quick and dirty.
4 stroke carburetors have an opposite designed system. They have a pilot jet which is immersed in fuel in the float bowl and a "T" but the front (air filter side of the carb) is open to the incoming air drawing across the top of the "T" and then the downstream (engine) side has an adjustment screw in it to limit the fuel that can be drawn past it.
There is actually a very good reason for all this madness... 4 stroke engines are known for their torque 2 strokes are not. For that reason, 2 strokes spend a lot of time with the throttle pegged "to stay on the pipe" so low throttle angles don't require as accurate a fuel metering. The air needle style adjustment works fine.
4 stroke engines need to be able to accurately meter fuel even at low throttle angles because they're torquey and stay at low throttle angles more. The way their carburetors are designed allows for multiple fuel outlets just behind the butterfly/slide which will open to allow more fuel into the carburetor bore as the throttle is held at low throttle positions. Unfortunately, this design doesn't lend itself well to the simple "air needle" design pilot system.
In summation, it's MUCH more common for a 4 stroke pilot system to clog than a 2 stroke pilot system. Most of the time idle problems on a 2 stroke are attributed to an EXTREMELY dirty carb or an airleak. 4 stroke carbs are nearly always at fault on the pilot system.
