Model a like a spirited colt or a carburetor problem?

[verrece]

The problem I have is, when the engine is at idle, it looks like a galloping horse, indepently of the best position of the air idle adjust screw. But above 800 rpm the engine runs properly.
After I disassemble the carburetor, I saw that when the throttle plate (butterfly) is closed (in their rest place), it blocks ups a half of the idle hole in the carburetor throat.
Anyone could tell me if when the Throttle plate is closed , the correct position should block the hole completely? or should leave completely open the idle hole? Or as I have now, it should block half the hole?
Could this “half hole blocks” be the cause of the engine gallop?.
The carburetor passageways were cleaned, I followed the Tom Endy´s article.
Any advice will be appreciated.