What a very timely post! I just came home from a weekend with my cart (a 1992) doing the same thing. Same as you, my brushes look fine. Have not had an oportunity to tear into the starter/generator yet, but, I may not even need to. My next guess (if the brushes really are fine-not sure how long they should be), would be the voltage regulator?

I assume you have checked all of your grounds, and not sure if this matters, but the fuse? I did on mine thay all seem (ohm meter and visual check) to be fine with excellent continuity. 

So, help us out folks, what gives? Do I (we) need to measure up the brushes and report back?

My cart is up at the cabin, and I only brought back the starter/gen thinking it needed just a brush swap out, but as mentioned earlier, my brushes look fine as well. I played charge and swap out the battery all weekend. 

Thanks, not trying to muscle in on your thread, but it sure sounds like we have the same problem!