That sucks, I just wrote a bunch of good stuff about KTM 640 reliability. I take it all back....
Make sure you peen the shafts for the new bearings in place. I didn't and paid for it when the shaft drifted out and raised a little hell.
Run a magnet around in the recesses. Check the water pump.
'02 KTM 640 Adventure-lowered
"On the road there are no special cases."
Cormack McCarthy-The Crossing
The faster it goes the faster it breaks.
And high performance=high maintenance.