john1c,
Looks like a shorted rotor, probably the most common failure in the XS650 electrical system.
My recommendation is to get a replacement rewound rotor from Custom Rewind in Birmingham, AL 800-798-7282. Talk to Gary. The rewound rotor is $125 plus your core, so it is important that you use the proper rotor puller tool so you do not damage the rotor. That tool is available from
www.mikesxs.com for $11. Sometimes Gary at Custom Rewind has a puller that he can loan to you. Talk to Gary.
Meanwhile, lets be sure that your rotor is in fact shorted.
1. Did you use the lowest range on your Ohmmeter? Typically 200 Ohms.
2. Go to Radio Shack and buy 2 10 Ohm resistors.
3. Connect the resistors in parallel.
4. Measure the resistance of the two resistors in parallel.
5. Should be 5 Ohms.
This little test will verify that your meter is working properly and that you did the measurement correctly before you blow $125 + shipping.
Additional notes.
1. I would suggest that you do not buy a used rotor on EBay. That's a real crap shoot. Likewise, do not buy a new rotor. In other words, you might find cheaper, and you can definitely find more expensive rotors, but you can't find a better rotor than Custom Rewind.
2. Be sure to remove the nut on the crankshaft before using the puller to remove the rotor.