Must jump starter

Schematic of a mtd riding mower from battery to starter

I have a 600 series yard machine and a couple of weeks back when I turned the key to start it, it acted like the battery was dead. I jumped it off from my car with no problem. I had planned to charge the battery but forgot. The next week when I went to mow the yard, again it acted like a dead...

How do you remove a starter.. I noticed the positive is on the side.. easy enough.. there are two screws under the starter.. is this how you would remove it? I don't see any other screws on it.. help!

I bought a used Ford 1210 compact tractor and it will not start with the key. I replaced the switch and still no luck. Tested the safety switch & wire that goes to the starter and both are in good order (verified with ohm meter). When I try to start with the key, the lights dim some so I can see...