The problem with the 640 is that it begs to be ridden just a little harder than other bikes due to its awesome performance and suspension. After a recent 5 day sortie through the mountain kingdom followed by a few local rides, I noticed my pelican top box was rattling a bit. Anyway, turns out the frame was cracked. Googled the problem and it seems to be a known 640 issue with many other cracking in exactly the same place, just behind the rear exhaust mounting. Looks like this after a little cleanup.