I don't want to beat a dead horse, but my curiosity got the best of me this afternoon and I tore apart the Zama carb.
It seems they did away with two separate fuel controls [needles] and drilled the high, medium, and low speed passages common to one needle. Then they drill two fairly large air bleed holes in the throttle plate. I mounted the carb back on the Homelite 25 and run it again after I plugged the two throttle plate holes to slow down the idle.
If the mixture is adjusted for a good idle, the engine accelerates to about 2700 rpms and dies. If the engine is adjusted to high speed, which it never really reaches as the orifices are too small and it is still lean, then the engine wont idle because it is too rich.
I allways wondered how they kept rpm down with a string trimmer with no load.
As most of you allready know, they have found a way to lean out a carb and keep a string trimmer allmost fool proof.
I just purchased a Walbro two needle 11.1 mm for just over $6.00 plus shipping.
Into the junk bucket goes the Zama.

FWIW, I know how they work and maybe it might save someone else some frustration.