B7100 Starter won't stop cranking

[Notamechanic]

When I turn the key to start my terrific old B7100 the starter just keeps on cranking. I have to disconnect the battery terminal to get it to stop. This happened after I replaced the starter solenoid. The solenoid arm has a little "hook" on the end. It came off easily but I think I may have reassembled it incorrectly? Is that little hook supposed to grab onto something? It looked easy ......now I'm in trouble.
Help!!!!

 

[Tooljunkie]

The most common solenoid failure when replacing is to over-tighten electrical connections. By turning either stud you energize the adjacent one. Its fine intil plunger activates solenoid, then it remains energized internally.

Been there done that.
I use 1/4" drive for installing electrical connections on starters.

 

[Dave_eng]

The little hook usually grabs unto the arm that pulls the starter drive gear into the flywheel.
Remove the starter and check this.
Also bench test it and see if it will stop when you remove power to the small terminal on the solenoid.
Dave M7040