Everytime I go to shut it off, I'm getting a backfire through the exhaust and/or carb. I hear a "Woof". It happens at all riding speeds and my air filter is clean. The plug looks good, any suggestions?

 

This is normal. It amounts to little more than unburnt fuel getting in the exhaust system when you shut down the motor. The heat from the exhaust makes the gas go poof when it vaporizes in the pipe. Mine does the same think.