Ryobi 725r "EZ"...can open partial choke to B but not to C?

Ryobi 725r "EZ"...can open partial choke to B but not to C?
I have a Ryobi 725r and am literally pulling my arm off
trying to get it to run fully. I have replaced the plug with correct gap .020; cleaned air filter: new fuel lines; new and correct fuel mixture 32:1. I am able to start it and move the choke to lower B position but am
not able to open the choke to the full run position C.
It will start easily, but dies if I don't set the idle up.
The engine has power but I am unable to figure it out.
It is in practially new condition. I don't know when it was made. I am on fixed income and trying to do it myself. Any help that you could give me would be
greatly appreciated and grateful!!
THANK YOU IN ADVANCE FOR YOUR TIME AND ATTENTION!!!!!!!!!!!