You sent a couple of emails without model or type numbers, and I won't waste my time guessing what you've got. Now that you have numbers in your posting, I'll try to explain. Since you don't seem to have an understanding of the fuel circuit, it sounds as if you are taking a shotgun approach to trouble shooting and changing parts one after another.

Briggs doesn't call it a "main jet", but they still have one in this carb. Fuel come from the tank via the long pipe 391813 pulled by vacuum thru the diaphragm pump 270086 and spring 260455. The diaphragm both pumps fuel up and has flapper check valves to prevent fuel flowing backward. The fuel them dumps into a small secondary well in the tank. From there fuel is sucked into the carb via the short pipe 296811 and into the main nozzle. What you call the "main jet" consists of the needle seat 2305911 and the needle 23433.

I'm assuming the two pipes flow freely. Check by blowing through them. Next you need to remove the needle 23433, needle-nut 230590, and the seat 230591. Behind the seat you will see two fixed orifices. The larger is for high speed fuel flow, and the smaller for idle. Make sure they are not blocked by running a fine wire through each or use a welding torch cleaner. Do not enlarge the holes.

After you reassemble, the needle valve is gently turned all the way down, and backed out 1 1/2 turns for initial setting. Do not crank down too hard, or you will damage needle and seat. After engine starts and runs, warm up and final adjust needle. Correct setting will allow engine to accelerate without stumbling when you snap throttle, but not run rough at high speed. I prefer to be slightly rich when testing at no-load (add'l 1/8 turn), to compensate for when engine is operating under actual working loads.

Refer to the attached PDF of the Briggs parts list.

Here is a link that might be useful: Briggs 130200 Parts List

It's the needle, ref# 118 on the IPL, page 4

Hello Bill, This is great ..... Thanks for the detail. I removed what looks like a brass main jet behind the needle and set assembly. It was partially blocked, so I ran it thru with the proper size wire feeler in my gauge set. Then I reassembled, set adj, at 1 1/2 tuns out and started the engine. After it warmed up, I could push the choke almost all the way open at idle. This seems to have corrected the overall lean condition.
Bill, What is this Stuff about "two fixed orifices"? All I noted was the Brass jet, is there something I am Missing? Please, explain .... Thanks, Jim.

I'm not the one that said anything about 2 fixed orifices.

Something else I would do however is to replace the diaphragm, ref 394?.
They can get stiff or torn and not "pump" the fuel properly.
They are only a $3-4 part at the dealer, so no sense paying twice that online for S&H!
Under the diaphragm, there are 2 holes-
One goes to the fuel pick up tube in the tank and the other will go to the venturi. The pick up tube has a screen on the end that could be getting restricted.
Use the plastic spray tube on your can of carb cleaner to blow out those passages. You should hear them "vent". One in the tank and the other in the intake/venturi area.

Usually, removing the muffler will make the diaphragm replacement much easier, because it will allow you to get a straight shot at the cover plate screws and make it less likely to strip out the screw heads.
Just pay attention to how the diaphragm spring etc. is arranged and re-install the same way.

ANother possibility for lean running could be vacuum leaks. I assume this is a rather old engine. Sometimes the throttle shaft can get worn in the holes and leak air there.

Just something to add to Bill's info. You may be referring to the two holes that go through into the venturi which are behind the brass seat. Also a tip when changing the diaphragm- lean the unit against something secure so that the cover is facing somewhat up before removing the cover screws. Even 25 degrees helps to hold the spring and cup in the socket and it is less worry of them going AWOL on you.

THANKS GUYS, for the additional information. Jim.

I just wanted to say thanks for this thread and advice. I'm working on the same engine and the advice given here helped me solve some problems. Thx.