I am at a loss here.
BEFORE I GET MY HEAD CHEWED OFF, I have searched Google and forums for the past 5 days and have not found someone with my exact issue and/or same engine size and brand.

So we got it from a friend for free (SCORE!!!) and had very very little issues from the start. Then, one day it died on my son and it has not started or cranked since. Tried jump it off, nothing. Tried jumping the solenoid wires, nothing. Tried going from starter straight to the battery, nothing. It is acting like it has zero power and yet I have 12v to the starter as I'm hitting the ignition switch. After letting my jump box sit on it for about 2 minutes, you could hear a very high pitched "squeal" as the starter attempted to turn and got it to turn maybe a quarter to a third of a turn and that's it. I know it has to be something simple and cannot find a picture of a wiring diagram that isn't super pixelated when you barely zoom in.

 

This seems fairly similar to me https://atvconnection.com/forums/1-e...e-problem.html take the advice I have just given there and get back if that doesn't fix it.