Unidentified noise

[rossmallett]

So I have this strange noise when I ride. I can only describe it as a metallic whipping sound. At first I thought the centre stand or similar was hitting the road but that doesn't appear to be the case. It's not specific to any gear or speed, doesn't do it all the time, nor when it is idling or revved on the stand, it's only when moving. I don't know if it's coming from the engine or somewhere else: there is no performance issue when it happens or any feedback through the throttle or bars, it's just this loud whipping noise which only lasts for a second or so. Any ideas please?