Small Engines (Lawn Mowers, etc.): Followup to weedeater repair qustion, lean mixture, grass trimmer

Question
Carburetor adjustment has been performed numerous times. No help there. Spark arrestor screen clean. Walbro carb. Unit acts like it is starving for fuel. This has now become a bit of an academic problem for me. I also tried running and adjusting unit in partial choke mode to see if a rich or lean mixture existed. Unit runs best with no choke. Truly tested in Tennessee.
Rick
 
-------------------------

Followup To

Question -
08/18 answer received. Cylinder and piston seem ok--unable to see all of cylinder/piston. No muffler carbon. Did not run weedeater w/ muffler off. Cleaned carb again, all orifices clear. Wondering if plug replacement may work. Engine revs but will not reach full power or revs,has good throttle response, occasionally bogs with sudden full throttle application, barely enough power to cut light grass. Trimmer not useful at this point. Will try new plug. Air-definitely Ok, gas-definitely OK, spark-seems OK, unable to check quality of spark other than color which seems ok also. I am frustrated as I am usually able to fix 2 cycle engines. Possible diaphragm pinhole? Weak spark? Cylinder scoring? Any other suggestions?

Answer -
 Hello Rick:

 While Holding the Engine at Full Throttle, Adjust the High Air Mixture Screw In Until the Engine Revs Properly. Was the Spark Arrestor Screen Clean? What Type of Carburator is On the Engine, Please? Thanks.

 Respectfully

 John

Answer
 Hello Rick:

 The Carburator Pump Needle May be Set to Low. It May Not be Opening Enough to Give the Carburator Enough Gas to Rev. If the Carburator is Clean and the Compression is Above 70PSI and the Exhaust and Muffler are Clear, then thats the Only thing Left that I can think of that would Cause the Problem of the Engine Starving for Gas going to High Revs. Send me the Carburator Numbers and I May be Able to Locate a Breakdown with the Specifications for Setting the Pump Needle. Hope this Helps. Let me Know what Happens, Please. I enjoy knowing the Outcome. Thanks.