mine is an 03 and i ride it to hell and backa nd it has never had any frame cracking issues.

 

I also have to agree with honda being super reiliable, but in a different dirtwheelers mag i was reading, there was a guy jumping his z400 at a local track after a day of riding he finally broke the frame. I looked at the pic from him jumping im suprised the frame or the suspension didnt give after two jumps, that guy was going pretty big. keep in mind the z was all stock