Yeah, that was my first thought, maybe something simple like no coolant. Assuming there is coolant, you might try after starting it up feeling the radiator hoses over on the left side of the bike. I once had similar quick overheating symptoms that turned out to be due to a grenaded impeller, causing no circulation of coolant. i recall one (can't remember now which) of the hoses stayed cold as a result. Just a thought. But given that you just got it, maybe you'll get lucky and it will just need coolant. Good luck.
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-Jim
'93 MC21