Small Engines (Lawn Mowers, etc.): Engine will only runs with full choke, air mixture, air screw

Question
I recently rebuilt the carb in my Briggs 18HP Twin V Model 422700 engine.  I also replaced one of the governor springs which was very rusted.  My problem is now I can't run the engine without using the choke.  I have tried adjusting the mixture but no luck.  I am wondering is when I replaced the governor spring I messed up the adjustment or whether I need to soak and rebuild the carb again.  If you could point me in the right direction I would be very grateful.  
Thanks,
Julian

Answer
Hello Julian:

You can View a Breakdown/IPL of this Engine at this Site Addy, http://www.smallenginepartswarehouse.com/parts.asp and Select the Shop Online Parts Look Up. Then Select the Model Tab. Then Select the OEM and Enter the Model Numbers (I used 422707). Then Double Click on the Model in the Results Area. Now you can Select the Section of the Engine you Wish to View. According to the Breakdown, there is Only an Idle Air Mixture Screw. You May have the Air Mixture Screw Adjusted Incorrectly. Here are the Instructions. Set the One Air Mixture Screw the Same as if there are 2 Air Mixture Screws. All the Carburetor Adjustments are the Same for Lawn Mower and Trimmers. There are Several Location for the Air Mixture Screws. The Idle Air Mixture Screws are Usually Located at the Top of the Carburetor Bowl and the Top of the Carburetor Body. If the Main Air and Idle Air Mixture Screws are Side by Side on the Side of the Carburetor, then the Idle Air is the Farthest from the Engine. The Main Jet Air Mixture Screw is Located in the Bottom of the Carburetor Bowl or Beside the Idle Air Screw on the Side of the Carburetor Body. Some of the Older Model Carburetors have the Main Jet Mixture Screw Straight in from the Top of the Carburetor Body (this is Rare anymore). If you have Cleaned the Carburetor (Disassembled and Soaked Overnight in Carburetor Cleaner (I Use Gunk). Then Blow Out the Passages with Compressed Air and Install a New Kit if Required. Now Setting the Air Mixture Screws:  ****Turn the Idle Air and Main Air Mixture Screws In Until SNUG **Don Not Jam** Then Reverse Both Screws 1 1/2 Turns. Holding the Throttle Full Open, Start the Engine. Turn the Main Air Mixture Screw Clockwise Until Proper Revs are Obtained. Occasionally you May have to Turn this Counter Clockwise to Achieve the Proper Revs. Now Allow the Engine to Idle. Set the Engine Idle Screw (Not Idle Air) so the Engine will Stay Running if Required. Now Set the Idle Air Mixture Screw so there is No Hesitation when Throttling from Idle to Full Throttle. Reset the Engine Idle if Required.**** If Setting the Idle Air Mixture Screw Does Not Help, then Make Sure the Fuel Pump was Assembled Correctly and there are No Damaged Intake Gaskets. What is the Cylinder Compression fo Both Cylinders? Is the Compression the Same or Close to the Same for Both Cylinders (75 to 80psi Minimum)? If you Did Not Soak the Carburetor when you Cleaned it, then the Carburetor can Still be the Cause.  Remove, Disassemble and Soak the Carburetor Overnight in Carburetor Cleaner (I Use Gunk). I have Found that Most People can Use a Breakdown/IPL and Disassemble the Carburetor Enough for Proper Cleaning. You Only have to Remove the Bowl, Float Pin, Float and Needle Valve and Any Adjustment Screws that Go Into the Carburetor Body. The Welch Plugs Do Not have to be Removed. Then Soak the Carburetor Body and Parts in a 1 Gallon Can of Gunk Carburetor Cleaner Overnight. The Can has a Parts Tray Inside it for the Small Parts. Once the Carburetor and Parts are in the Cleaner, you can Replace the Lid for Safety and to Prevent Accidental Spillage. Then Blow Out the Passages with Compressed Air. Install New Parts if Required. The Spring you Replaced is a Part of the Throttle and Governor System on the Engine. The Spring Pulling on the Governor Arm Either Directly or through a Series of Pivots Maintains the Engine at the RPM the Throttle is Set at. Hope this Helps. I am Here if You Require More Assistance. Let me Know What Happens, Please. Thanks.

Good Luck

Respectfully

John

PS: I am Allowed to Answer 10 Questions a Day. If you See I am Maxxed Out, then Try Submitting you Question at or Just After 9pm EST (US). My New Day Starts then. Thanks.

Respectfully

John