Everything is working, it’s just your image itself that is causing it to look like that, not the theme/site. Take a look at your image – http://superiormotorcycles.com.au/wp-content/uploads/2015/03/superior-logo.png you’ll see it’s not centered directly in the middle.
It is centered in the middle of the actual theme (the CSS), it’s just the image itself that needs to be re-edited in photoshop to be centered. Make sure and remove any extra transparent space on both sides, and that will fix it.