Wow - that is quite a tear-down for a dirt floor garage - holy heck!
I'm getting the same noise as other's here have described. And as someone else mentioned, it almost sounds like its coming up from around the guage cluster.
I think what PlecoLB is describing is far different from the rattle that I hear.
You said: "When I bought it, it had a high pitched rattle noise at about 4000RPM while cruising / coasting. Its gone under power.
I now have what I can only describe as a stretched chain noise from low revs all the way up while coasting / cruising. Gone when I pull the clutch and drop the revs while rolling. "
Does that mean the rattle went away and then several thousand miles later you have the "stretched chain noise" ?
Could it be the two are/were separate issues.
I guess the last thing I'm going to do is tear down a new bike in search of a noise that was happening on a 150000 km bike. Most everyone here is complaining about the noise on fairly new machines with lower miles. I don't know......I won't let this new info make me paranoid. I'm gonna run it like a crazy ape and not look back.