Whelp! I found the problem.

No, I didn’t get any of those. Don’t recall seeing any of them in any of the boxes of stuff either. My theory is that the complete bike that was there had a blown motor (the whole bike was in awful condition, and I noticed a massive skid on one of the case covers) and so the spare motor was bought to replace it. They would’ve likely reused the original harness and whatnot. I could be wrong, there was also nearly a complete bike in additional loose spare parts as well. They did say I could come back and buy more if want to. But given the condition of everything I saw, I’m mostly inclined to source other parts I need from elsewhere. 

Plugs came out easily, and the motor turns over freely.