400ex cam ?

[mjd400ex]

can the decompression unit go bad on the cam,on a 400ex can they make noise?

[Jared Coderre]

Yes, it's possible. Are you sure it's that? More likely a cam chain tensioner. If you do find out its the decompression mechanism. You can have my old one. I went with a stage 1 recently and no longer need it.