Repair-It

And further diagnosis...

I have this:
https://www.advrider.com/f/threads/comp ... wn.737875/

Oddly this didn't really seem to do much. I suppose a good test would be if my inverter generator can start it up and run it. Last time it totally refused. So if that works, then I can definitely claim success on the capacitor replacement.

I ended up taking the rotor out. I lubricated the rear bushing with some wheel bearing grease and oiled the front bearing. The bearing is worn and somewhat sloppy but rotated with no friction. The rear bushing was dry, though.

I think the next step is to finally run a dedicated 20A circuit for the air compressor. That's been on the list since we moved in.

Finally ran a dedicated 20A circuit, almost 9 years later. Used a GFCI outlet. Runs out good. No more flickering lights and it sounds pretty healthy now.