Motorcycle Repair: zxr4, exhaust noise, calipers

Question
I have a nasty rattle that has just started.
it sounds almost as there is something stuck in the break calipers but these are clear. It only appears when in motion. I have my own thoughts but i am no expert, i was thinking it may be the seater rubber that has gone...?

Answer
Sorry, but from your short description I have no idea what you are talking about. "Rattles" can be dozens of things.  If you want to tell me more specifics I can guess at it.  What area of the bike? Hot or cold?  Does it happen at certain speeds or rpm?  Do you hear it when you apply the brakes.  Try shutting the engine off and coasting so you can hear it more clearly without any engine or exhaust noise.  Is your kickstand spring tight?  And what is a zxr4?  I'm a Harley mechanic!!