Welcome to TBN, Steve
If you go back to page 160 of this long thread, I have posted my replacement wiring diagram.
I don't know what they are using for an ignition switch in your unit, but the replacements I have used in the 3 units I have rewired has the logic of a riding mower switch. You will need to figure out the logic of your switch and trace the wiring to see why the ignition seems to be grounded when you are trying to run the starter motor.
Update:
The switches I used were STENS 430-706 ($20), which is a 5-terminal riding mower ignition switch. I see the AgroTK website sells replacement switches ($45!) that are only 4-terminal units.