I just bought a 04 600rr and am having horrible shaking and vibrating when hitting the rear brakes. At first i thought it was the front but i got the bike up to about 45 or 50mph hit the front brake hard and it did not do it. The next time i got on it and got on both the brakes and it violently shook until i let off the rear brakes. It feels like something is rubbing badly but i cant find the problem. The rear brake looks ok besides the top bolt on the left seems slightly bent, but everything was tight. Anyone know what it is?

 

What does your rotor look like? Does the whole bike shake or just the rear end? Does the rear feel like it's sliding out?