Small Engines (Lawn Mowers, etc.): Carberator problem, mineral spirits, exhaust port

Question
I have a Zama C1U-H46 Simple Start carb on a John Deere trimmer I am fixing for a co-worker.  The trimmer wouldn't start but would start with starting fluid and then die out.  This guys air filter had disintegrated so I took the carb apart and soaked it in mineral spirits.  There was obvious dirt inside the carb.  I decided since I had it apart I would rebuild the carb for him replace the fuel lines and fuel filter.  I ordered a rebuild kit.  The kit wasn't exactly the same so I only changed the needle valve/spring, diaphragm and welch plate.  In the new kit (RB-26) the pump diaphragm didn't have the same holes as the old one so I left the old one in.  The old pump diaphragm was intact and not broken.  Now when I start the trimmer, with the throttle wide open the motor runs at a low idle.  I have adjusted the low and high in every position imaginable.  When I press the primer bulb with the unit running the unit revs up and then goes back down to a low idle.  When I release the throttle the trimmer dies.  I have taken the carb apart about 10 times looking for the cause checking the jets and ports for blockage blowing air through it and still it does the same thing.  I even tried putting the old diaphragm back in and when I do that it won't start at all.  At this point I think it's time for a new carb.  Do you if I have overlooked anything?

Answer
Hello Don:

Have you Checked the Exhaust Port and Muffler for Blockage? If the Muffler or Exhaust Port are Restricted, you will have the Problem you Described. 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. 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. Ratings and Comments are Greatly Appreciated. Thanks.

Respectfully

John

Hello Again Don:

I Failed to Mention, if the Exhaust Port and Muffler are Not Restricted, then the Metering Pump Needle May be Set Wrong. The Information for Setting the Metering Pump Needle is in the Technical Guide at the Site Addy I am Including. I Forgot to give you a Site Addy that Might Assist you Also. You can View a Breakdown/IPL of the Carburetor and Get Technical Information on Zama Carburetors at this Site Addy; http://www.zamacarb.com/tips.html and Select the Technical Guide. 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. Ratings and Comments are Greatly Appreciated. Thanks.

Respectfully

John