Small Engines (Lawn Mowers, etc.): Grasstrimmer starts wont run., ryobi 725r, maintenance mechanic

Question
I have a Ryobi 725r 31cc grasstrimmer.  It will start and idle with the throttle in the "A" or start position.  As soon as I switch it to the "B" or run position it revs up and cuts off.  I have adjusted the two fuel settings.  The tops of the screws are are colored white and red.  Not sure what they are called.  I replaced all the fuel lines and fuel filter.  I've flushed the carburetor with cleaner.  What else can I try to keep it running?

Answer
Hello Phil, you doing what any preventative maintenance mechanic would do. Sounds to me that you have an excellent handle on everything. Make you adjustments, when the engine is running and be patient let it run for a while and do not work the machine until you get the desired speed. You also have a primer bulb on there. What a primer bulb does is forces extra fuel into the carburetor intake. Also another key is get you hands on the operator manual.