Justin Bieber: Drink and Ditch On Pricey Scotch Tab

Justin Bieber is not as smooth as Tennessee whiskey -- or scotch for that matter -- because he bailed on a $130 bar tab after a heated exchange that nearly turned into a bar brawl.

Justin kicked off his tour in Seattle Wednesday night, but on Sunday night he and 7 pals hit up The Whisky Bar and ordered a round of shots. Sources at the bar tell us they asked for a mid-range blend and got GlenDronach ... a 12-year-old single malt scotch, $15 per shot.

We're told the group went out for a smoke and never came back to pay the bill, but they were all caught on surveillance cams.

One member of JB's entourage tells us trouble started when a female fan wanted a pic, but was denied by one of Bieber's dancers. That's when a guy with her got pissed, and started yelling and making a scene. We're told Justin's group decided it was best to get outta Dodge before a fight started.

Our source says one of Justin's bodyguards was supposed to pay, but obviously didn't in the chaos. We're told they settled up with the bar Wednesday night.

Bottoms up.