My CBR had the same rattle. It had something to do with gear driven cams, so dont sweat it.
Your bike might be running a bit rich, misfiring on a cylinder and have a blockage in one of the carbs. Check the plugs and replace all of them if you think you need to. Alyhough, the way you describe it stalling and then returning to full power makes me think fuel blockage....
Good luck
To every man upon this earth
Death cometh sooner or late
And how can a man die better
Than facing fearful odds
For the ashes of his fathers
And the temples of his Gods
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