Hi Lucas & welcome to Ninjette!
You need to measure actual battery-voltage to determine state of battery.
Measure again as you push START button; actual voltage-drop is sign of battery-health.
And pull each and every fuse and measure its resistance with multimeter. There is no "looks OK" test for fuse, only objective and quantifiable test is number of ohms resistance between legs as measured by multimeter.
https://learn.sparkfun.com/tutorials...multimeter/all
If I had penny for every time I've heard fuse "looks OK" and it actually didn't conduct electricity...
Well, I know it has cost me thou$and$ of dollar$...