He's a 'mechanical' genius. [=he is a person who is very smart about machines]
He's not 'mechanically' inclined. [=he is not knowledgeable about machinery]
The flight was delayed because of 'mechanical' problems/difficulties.
(..) - Yep. All that's missing is a ginger midget. They cleared something away from here. Not minutes ago. Like what? I'm not sure. Something mechanical. Holmes, look at this. - Chapter and verse. Revelations. . "I am here liveth - and was dead." (..)2009 Sherlock Holmes