Annoying Gap in Menu Bar - Mavericks

Hold the command key and drag it to the far left or off completely.

SystemUIServer is the background process that specifically controls the right hand side of the menu bar where those menu extras are. So deleting that preference will reset your menubar to default. But since your active menu bar seems correct, I don't know if it will have nay effect.

Go to your Finder "Go" menu hold the option key to choose "Library". Then go to the Preferences folder and find and delete com.apple.systemuiserver.plist. Then go to the By Host folder also inside your Preferences folder and delete com.apple.systemuiserver.plist (also any with numbers). Then log out and back in, or restart.

Did you try to deactivate all the apps at the top? I would suggest you disable their appearance in the top bar, shut them all down, take them out of the boot items and then reboot. After that your bar should be clean. Restart the apps on after another an set them in the top bar again. With this approach you can identify the App causing the annoyance. But that's just a hint.

Check your boot items. It could also be an App that starts with OS X and crashes at one point, leaving a blank spot.

PS: dont forget to disable Timemachine and Airplay in the top bar, they could also be source of your problem...

What do you mean systemuiserver prefs did nothing... They didn't set the right side back to default, or when you added back the menu extras the gap was still there?

I've got this issue too and can't seem to get it sorted. Its not too much of an problem but would rather my menu bar looked all neat and tidy!!

I'd like to chime in and say that I now am also experiencing this problem, but with Yosemite. I can't seem to shake the problem off...