Scag mower won't start

[fosteronomo]

My Scag STC48A-19KA is not starting. There's a chipmunk whir/clicking sound from the solenoid. Some tries at starting get me a single clack from the starter but that's it.

Any suggestions on what to replace first?

UPDATE

I pulled the starter and bench tested it with jumper cables. It's not turning. Guess I found the problem.