Originally Posted by Retro Grouch

A ham fisted chimpanzee can be trained to adjust rear derailleurs. Fronts, on the other hand, require a bit more precision.

1. If it ain't broke, don't fix it. Since "it changes perfectly on and off the center ring" I'd leave it alone.

2. Every front derailleur adjustment affects the subsequent adjustments. If you decide to fiddle with it my advice is to disconnect the shift cable and start from the very beginning as if you are installing the derailleur for the first time. Park Tool has a good set of step-by-step instructions. Follow them in sequence.

Good luck.