Starter not engaging

I have a 1981 Kawasaki KZ440. The brushes went bad in my starter I rebuilt the starter and tested it with a battery charger. I reinstalled it and it just spins. It does not engage.

Need to rebuild the clutch.
Steve

I had a similar problem,starter was just spinning.I pulled the starter and it was fine,pulled off the left side cover and found my rotor bolt came loose and the gear that connected to the starter gear was just spinning.Tightened up the bolt and its been fine since.