Small Engines (Lawn Mowers, etc.): carburator, air mixture, three needles

Question
I have a murray 42" with a 229 carb on it. How do I tune the carb
idling to rich and sometimes backfiring. How many turns and which of the three needles do I turn.
Thank you

Answer
Hello Frances:

>>Sorry for the Delay. This Question was Located in the Question Pool and I can Only Answer Questions from the Question Pool when I am Not Answering Questions here or at the Other Site I Answer Questions at.
>>The Following is an Instruction File I made for Correcting this Problem. Any Input is Appreciated.
>>****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 Nearest to 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.
>>The Engine Idle Screw is Usually Easy to Identify because you can See where it Makes Contact with the Carburetor Throttle Shaft Plate Stop Ear. The H and L Air Mixture Screws Go Into the Body of the Carburetor and the Tips Cannot be Seen.
>>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 **Do 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 This Carburetor has a Single Air Adjustment.
>>Use the Section Above that Pertains to Full Throttle RPM Air Mixture Screw and then Adjust the Screw if Required to Eliminate Any Hesitation when Rapidly Throttling from Idle to Full Throttle.**
>>1- http://www.repairfaq.org/samnew/lmfaq/lmclctc.htm   
>>2- http://www.cpdonline.com/692509.pdf   .
>>You can View a Breakdown of this Mower At this Site Addy; http://www.smallenginepartswarehouse.com/parts.asp and Select Shop Online Parts Lookup. Select the Model Tab. Select the OEM and Enter the Model Numbers (). Now Double Click on your Model in the Results Area. Now Select Sectional View. Now Select the Section of the Mower you Wish to View.   
>>If you Hit a Snag or this Does Not Correct the Problem,  I Hope to be Here if You Require More Assistance. Hope this Helps. Let me Know What Happens, Please. May the All Mighty Bless You and Yours. Be Safe and Happy. Thanks.

Good Luck

Respectfully

John

PS: I am Allowed to Answer 5 Questions a Day. If you See I am Maxxed Out, then Try Submitting your Question at or Just After 8pm EST (US). My New Day Starts then. Comments and Ratings are Greatly Appreciated. Thanks.

Respectfully

John