Over the last year or so my XR has had this funky valvetrain noise intermittently when hot. I thought it was the auto-decompression unit activating when it's not suppose to but after 3 days of research and 2 teardowns later, I found it to be a loose exhaust valve seat!
I am way lucky I caught it when I did. It could have damaged ALOT of crap!
So now that I have no dunes AND no DS bike to ride I'm going crazy. I ordered my parts up tonight and will be dropping the head off tomorrow. The only good that is coming from this is the bike should run quieter, smoother and should run stronger. I am going to throw a hot cam in while I'm at it.