440 Starter issuses

[mstancer]

alright, getting my butt kicked by this 1958 440 John Deere Dozer. Parked it last year in the shed for the winter. This late summer went to pull it out and exercise it a bit around the yard, you know have some fun with it. Removed my battery out of my 630 bobcat, little 550 cc 12v battery, have a 6-volt starter original equipment in the dozer, went to start it, turned over a half turn or so, then acted like a dead battery. Battery is good not even a year old. but, just in case pulled the one out of the tractor, 12v 650cc. same result, barely turned over. Pulled the starter to bench tested, works great, engages and spins just fine. I know theirs no load on it, but seems to work great. Installed it back on the dozer, pulled battery out and set it to the side of the dozer. Hooked up the negative to the transmission grounding location, had the 2 positive terminals lay out, one off the starter, one off the battery. Used jumper cable to connect the positives together, so i could remove them quickly, the starter, started to turn over slowly, looked like i was starting to weld at the cable connections, instantly the cables started turning hot.
I know starter solenoid is trash, closes fine, when the starter is disconnected. connect it up it rattles for a bit then just stops altogether. Just try to see if i am completely over looking something. before i buy a starter or if that's even the right choice. Thanks for letting post this, any help would be great.