Poulan PP335 trimmer : Head spinns if idle speed is set high enough to keep it running ?

I have a Poulan PP335 that i just bought. I like it and it starts easy the only thing is that out of the box it would die out if the throttle wasn't held down. That was easy enough to fix by upping the idle speed a little BUT there doesn't seem to be a sweet spot on the idle speed screw that allows the engine to continue to run at idle without the trimmer head spinning at idle..... The trimmer will run fine at at idle but if i back the idle set screw off just a hair to stop the head spinning, the engine dies out again. Is there something I'm missing or is this an issue that I should refer to a small engine shop for some sort of carburetor adjustment, or should i just let the trimmer head spin and not worry about it?