Ihave a 99/400ex and the rear shock is making a really weird noise. when you push down on the seat it sound's like cracking.any one know what it could be. thank's for any imput on this matter.

 

Sounds like you have a linkage touching the skidplate, or the like. Maybe some dirt/grit/small rocks somewhere they shouldn't be, clean it up really good, have someone else push down while you pinpoint the source of the noise.

It's really hard to make a diagnosis with the info given, but I would check the items above first.