I have had a starter short internally, one of the long through bolts was the culprit, fixed the problem with heatshrink on the bolt/screw. If its been shorted a few times it may have blown the wire in two.
http://www.xs650.com/threads/shorted-starter-motor-and-a-fix-for-it.43610/
For the record that stater is still going strong.
http://www.xs650.com/threads/shorted-starter-motor-and-a-fix-for-it.43610/
For the record that stater is still going strong.