If you have battery voltage (or close to it) to the blue wire that energizes the solenoid that pretty much indicates a failed solenoid. The only other possibility would be a bad ground from the battery - to the frame/engine which is less likely. You indicated in an early post that the starter would turn with power applied directly so that pretty much eliminates the starter and points to the solenoid as well.
The discussion regarding cleaning and lube of the bendix/armature is valid for BF and B series engines where inertia throws the bendix out to engage the flywheel ring gear but the Performer and CCKA engines that Case Ingersoll used are solenoid shift starters (solenoid mounted on the starter) and the solenoid both acts as a relay to supply power to the starter motor plus physically pushes the bendix gear forward for engagement.
I took the Starter off and cleaned it up then sprayed the shaft with WD40. Reinstalled it and the Solenoid clicked when I turned the key to start but that was it. Jumped from batt + and the starter spun but never did engage. Took it off again, looked it over and put it back in again and it started with the jump? I dunno but the starter is one that I put together with other starter parts I had. I'm just going to order a new one. Thanks all for all your help!!! Doc
Just in case anyone is interested. I installed the new starter and all was back to normal as the engine started with the twist of the key. The solenoid on the old starter was tested and found to be bad! Thanks again to all who took an interest! Doc