Not starting, possible seizure?

[bmo1721]

Any help would be greatly appreciated. 2004 GS500F, 27,000 miles
When driving home a few days ago, my bike ran perfectly for about 10 minutes. All of a sudden when I downshifted, the bike lost a lot of power, and then stalled out. The rear wheel locked up for about 15 feet, and I was able to get it to the side safely. I tried bump-starting it in second gear multiple times, but every time I would let the clutch out, the rear wheel would lock up again, and it would sound like the clutch is grinding. Whenever I would try the starter button, I would only be greeted by a single click, and then it sounds like it is winding down. I called a friend over, and we tried bump-starting again, with the same issue. Then we tried to jump the bike from his truck (not running), but still, the starter would only click once. The next day, I came back to where I had the bike parked to discover the dipstick was reading no oil at all, it took 2qts exactly to bring it to full. I tried to bypass the starter by having the bike on, and then touching a screwdriver to the positive and negative of the starter solenoid. Some sparks, but only the single click. When the bike is on the center stand, and in gear, the wheel will not move even with the clutch in. When the bike is on the ground, it will move with the clutch in while in gear. Neutral moves easily both on the center stand, and on the ground. I am really hoping the engine is not seized. How could I check this, or what else should I check? Should I try manually turning the engine, and if so, what size socket would I need?

[mr72]

Stop trying to turn the motor over. It's siezed. Further effort to try and force it to turn over will likely break more things.

If you ran it out of oil then there's the smoking gun.

If I were you, the next thing I'd do is pull:

- the tank
- the carbs
- the head
- the jug

Then you will find the bent con rod or dropped valve or whatever. And you'll be able to see down into the crank and see the spun rod bearings.

Good news is, apart like this the engine is a lot lighter and easier to remove from the frame... so you can pull the crank and finish the rebuild