Mine did the same thing after the KLR fell over and that middle support bar(s) got shifted/bent and was making contact with my voltage regulator. Even though it was just barely touching it, it made a surprising amount of noise. Once I shifted/bent it back, the noise went away.
Might want to take a second look at the area where those overlapping flat bar things pass through around the frame, voltage regulator, fan etc. and see if there is any contact being made there. If there is, not only would it create an annoying buzz, but could eventually cause damage to whatever it's vibrating against.
I doubt if it's any of the joints on the bars themselves, rather some component of the bars making contact with a component on the bike. Another likely suspect is the clamp thing where those two support bars overlap and are attached to the frame.
Hope you're able to pinpoint the source of your problem. I'd be interested in hearing what was causing it.
Last edited by planalp; 07-08-2012 at 12:12 AM.