I was having a similar problem that also included the bike dying after I came back from a short but hot run. I noticed the fan wasn't kicking on and I was having to trickle charge my battery. Once I removed body pieces I found a bulging, gunked up hose at the overflow, low fluid in the radiator, reservoir full of old sludgy water, thermostat housing pretty rough looking. Cleaned everything up, cut back hoses, flushed radiator, also changed oil (it had been a while). Despite all of this, I just ran the bike for 10-15 minutes, the temp gauge didn't get up very high, although the bike felt warm, but the fan never kicked on and when I turned the bike off and tried to start it again, it was that same dead alternator kind of sound. Thoughts?