[351mustanger]

I'm sorry, my wording was not the best for someone that is learning. The main jet controls the fuel flow at wide open throttle. The fuel screw should be set to where it gives you the highest idle rpm (while the engine is at operating temperature). This setting should ideally be somewhere between 1-2 turns out from lightly seated. If it is less, the pilot jet is too large. If it is more, the pilot jet is too small.
I would warm the engine up and take note of the stock fuel screw position. You do this by turning the fuel screw in until it just stops, counting the turns it takes to get there. Do not put any torque on it or the screw or carb could be damaged.
Next set the fuel screw at 1.5 turns out from lightly seated and adjust the idle to the proper setting. Then slowly turn the fuel screw in or out until the idle rises to the highest rpm. once you have reached the highest rpm, adjust the idle back to the proper setting. This should be the optimum fuel screw setting.
Next count the number of turns the fuel screw is backed out. Like stated above, less than one=get a smaller pilot jet, more than 2=get a larger pilot jet. If it is between 1 and 2 turns out, your pilot jet should be fine.
The questions asked by sycarms are important. Trying to tune the carburetor of an engine that is not in good mechanical condition is useless. You will need good compression, good spark, clean air filter, valves adjusted properly, fresh fuel, etc. etc.
what do you mean "when you try to touch the choke, it dies"? Choke it, and it dies? Or turn choke off, and it dies?