I'm afraid it does sound like you've seized it.

First thing to do to pull the lower fairing off and remove the exhaust pipes. Have a good look up the exhaust port and see what kind of condition the pistons are in.

By the sounds of it, it might not be a full seize but might of whiped a ring which you can sometimes (if rarely) get away with by cleaning the barrel and fitting a new piston.
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If I have to take the carbs off once more...