Have just bought me a z1000 and have discovered that there is an noise from the engine when the engine is cold. Disappears after 55 degrees. Adds video, where you hear the sound behind all the exhaust noise. https://youtu.be/VHs1doUdqDs
Honestly it sounds like some gear whine. It may disappear or change with temperature as things heat up, and/or the oil viscosity changes but it really sounds pretty normal. My Concours engine is very similar to your bike's and it sounds the same.
I think I know what your talking about, it sounds like if it was a loose belt or something right? But motorcycles don't have belts. Lol, My bike makes the same noise when I start it but I always thought it was normal, sorry don't know what it could be.