I had the usual "solenoid clicking but no start" problem and decided to get to the bottom of it. I made five videos, which I loaded into YouTube because of the size of each video, on how I tested each component and solved the problem. You can also search under Tre e Mezzo Parts 1 through 5 for them. Be warned: these are home made videos made by someone who is definitely not a Martin Scorcese....
Video 1: Testing the Solenoid: https://youtube.com/shorts/BcHdf0YEGOE?feature=share
Video 2: Dismantling the Starter Motor: https://youtube.com/shorts/etDyD3QoHbM?feature=share
Video 3: Armature Tests (Grounding, Bar-to-Bar, 180 degree, and Brush Continuity) https://youtu.be/_XmmJLtWoKc
Video 4: Examining the Carbon Brushes and Dimension of the Brushes: https://youtu.be/QDNxXhhH6x0
Video 5: Reassembly and Final Testing: https://youtu.be/qcVSfeF1AeA
Hope this is useful.
Joe