Small Engines (Lawn Mowers, etc.): Craftman (sears) trimmer 21cc, carburetor body, air screw

Question
I had my trimmer repaired by sears,unfortunately I tried to set the Carburetor by the two screws locate on top,1 for fuel mixture and 1 for idle screw,and got hem all out of tune,above all it has no limiter cap on the mixture screw if I turn it out it will come all the way out.now I have no starting point to adj it period,I have tried to screw them down,and then back it off 1 1/2 turns but it does not work,I used new bought gas and mixed it right,,40:1,and it has a new plug,and filter in the tank,so anyway I am at wits end wondering where to start now I have the manual but it does not tell you specific info on adjustments of carburetor,so I am running in the blind on this one.any advise thanks,

Answer
Hello James:

Lets Check the Muffler and Exhaust Port First and Make Sure they are Clear of Carbon. The Spark Arrestor Screen in the Muffler Must be Clear Also. A Restricted Exhaust Port or Muffler will Cause you to have Problems Setting the Carburetor Mixture. If these are Clear, then Use the Section of the Following Instructions that Pertain to the Carburetor Mixture Screw Setting. Set the Carburetor as if it had 2 (Idle Air and Main Jet) 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 **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.**** Hope this Helps. I am Here if You Require More Assistance. Let me Know What Happens, Please. Thanks.

Good Luck

Respectfully

John

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Respectfully

John