Small Engines (Lawn Mowers, etc.): trimmer wont starts easily but wont stay running, needle nose pliers, walbro carb

Question
John:  You previous advice got my Honda mower purring like a kitten. Now I need some magic with a trimmer.  The unit is a McCullouh Eager Beaver 282 with a Walbro carb. It starts on the 3rd pull but will only run for 10-20 seconds in the middle choke position. It doesn't smoke profusely on startup.I changed the plug, new fuel lines, carefully took apart the carb and cleaned it with carb cleaner, put in fresh gas. No difference. I have played with the mixture screws to no avail.  Any ideas.

Answer
Hello Bob:

Thanks for Returning. I am Glad to Hear your Mower is Running Properly. Now lets see if we can Assist with your Trimmer. Have you Checked the Exhaust Port and Muffler for Blockage? The Following is a Basic Instruction File for Doing a Diagnostic on the Engine for this Problem. Any Input is Appreciated. **Remove the Muffler and Make Sure the Exhaust Port is Clear. If it is, then Try to Start the engine with the Muffler Off. If it Starts and Runs Properly, then Clean the Spark Arrestor Screen in the Muffler or Replace the Muffler if Required. Have you Replaced the In Tank Filter? The Fuel Line is Pushed and Pulled (I Use Long Needle Nose Pliers) Through the Small Hole Until the Hose is Out the Fill Hole about a 1/2". Then Attach the Filter and Pull the Hose Back Until the Filter Lays at the Bottom of the Tank Just Below the Fill Hole. **Hint: Use Plenty of Spray Lubrication at the Small Hole as you are Feeding in the Hose. It Slides Easier.** The Following is the Instruction File for Setting the Air Mixture Screws. Any Input is Appreciated. The Procedure is the Same for 1 or 2 Mixture Screws, Just Use the Instruction File and Skip Over the Section with the Missing Mixture Screw. Now Setting the Air Mixture Screws:  ****Turn the Idle Air (L) and Main Air (H) 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 (H) 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 (L) Mixture Screw so there is No Hesitation when Throttling from Idle to Full Throttle. Reset the Engine Idle if Required.**** Did you Soak the Carburetor when you Cleaned it? If No, then the Carburetor can Still be Clogged. The Cost of the Cleaning Solution I Use is $30.00us @ Gallon (I Use Gunk). The Gallon Can Comes with a Tray for Small Parts and the Carburetor Fits Nicely. Most Times a Carburetor can be Soaked and Cleaned and with the Float, Needle Valve and Other Carburetor Components being Soaked in the Cleaner with the Carburetor Body; there are No Parts to Replace on this Carburetor. If you Soak and Clean this Carburetor and the Float Needle Valve Still Does Not Stop the Gas Flow Properly, then Purchase a Needle and Seat Kit and Replace it. The Following is a Basic File I Made for Cleaning Carburetors. Any Input is Appreciated. The Most Common Cause is; The Carburetors Internal Passages are Restricted by Varnish that Gas Forms Over Time. This Varnish is in Layers. To Properly Remove this Varnish you have to Soak the Carburetor. The Following is a General Instruction File for Carburetor Cleaning. Even though the Carburetor Looks Clean, the Internal Passages May be Restricted with Varnish that Gas Causes to Build Up over Time. I Suggest you Make Sure the Gas is Free Flowing to the Carburetor Inlet Port (if the Model does Not have a Fuel Pump). If the Gas is Free Flowing to the Inlet Port, then  **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 (if Applicable), Float Pin (if Applicable), Float (if Applicable), Needle Valve and Needle Valve Seat if Applicable. This is a Flat O-Ring Located in the Inlet Port the Float Needle Rests in. Use a Strong Wire with a Slight Bend to Remove the Old Seat. Sometimes a Small Pocket Screw Driver can be Use Also. The New Seat will have a Slightly Beveled Side and a Flat Side. The Flat Side goes Towards the Carburetor Body when Inserted into the Inlet Port. Spray the Seat with Spray Lubricant to make Installation Easier. The End of a Drill Bit that is Slightly Small than the Seat can be Use as an Insertion Tool. Wear Gloves or Use a Rag when Handling the Sharpened End of the Drill Bit. Remove 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.*** (Do Not Use High Pressure Air for the Zama Carburetors, they have Check Valves for the Primer and these are Usually Blown Out of the Carburetor if Not Careful. Allow the Zama Carburetor to Set on a Drip Pan and Dry)***. ****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 Nearest 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.**** 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 Throttling from Idle to Full Throttle. This file was Intended to Give you the Basic Carburetor Cleaning Instructions and May Not Reflect Your Carburetor Components. If you have Questions, Please Ask. You can View a Breakdown/IPL of the Carburetor at this Site Addy, http://69.16.165.8/ and Select Service & Aftermarket. Now Select Aftermarket Parts and Service. Now Select the OEM. Now Select Trimmer. Now Select your Carburetor from the List Provided. If you Hit a Snag or this Does Not Correct the Problem,  I am Here if You Require More Assistance. Hope this Helps. Let me Know What Happens, Please. May the All Mighty Bless You and Yours. 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 your Question at or Just After 8pm EST (US). My New Day Starts then. Thanks.

Respectfully

John