Okay here goes, I recently had a new drive belt put on at the dealer. I drove the bike 1300 miles with NO issues. Now when I let of the gas and then throttle up I hear a metal on metal bang. Only once does it bang. It's happening in all gears and the bang sound is louder the harder I accelerate. Nothing unusual on start up sound, only when I'm off an on the throttle. Once again there is no sound other than motor when in neutral revving. I opened the primary and found nothing loose, no visible wear and clear fluid. Tensioner working with no chain slack other than 5/8 or so movement. When I put the bike on the lift I can move the rear tire approximately 2/3 inches both ways with it in gear. The banging almost sounds like a bad u joint on a car??? Please help before I get raped at a dealership! Thanks...
Also there is no unusual sounds upon startup..

 

rear pulley tight ? loose compensatoror missing parts ? if it's not in the primary,start looking at the trans.