Case 580B backhoe won't crank - help!

So- I need to fix it myself.

Here's the Info:
Backhoe sat all winter unused at a friend's house last year. When he tried to start it, he said the solenoid was sticky- had to bang it to get it to engage.

Then it totally failed in the spring, so he replaced the solenoid. New battery as well. This worked fine until now.

Last night it cranked slower than normal, but did start. I did some work and shut it down. Then a few minutes later had to start it again- dead. No crank, no clunk.

I put a charger on the battery overnight just in case. This morning, no change. When I press the starter button, I do see the ammeter on the charger rise a bit. So this tells me that current is getting to the solenoid. The ignition light is bright and dims slightly when the starter is pressed.

I tapped it with a hammer while holding starter button to no effect.

So, I guess the starter comes off this weekend and I'll take apart and look for places to clean and lube. Any other suggestions?

I reckon maybe another test is to connect a hot wire to the solenoid, on the theory that the starter button is making poor contact.