Whirring sound when starting bike

[PaulJ]

When I press the start button the bike starts but it makes a weird whirring sound while the start button is being pushed. As soon as I let go the sound stops and the bike runs as usual. It's a 2011 xr650L. It's been doing it for while now and doesn't seem to be getting worse.
Any ideas?

 

[Dux]

 

[PaulJ]