I had this problem just about a week ago, battery read 12.60 enough to light everything up and start, but it didn't. After checking all connections and fuses same results. I turned the key on and then checked the battery and it only read 1.20 indicating a short in the battery itself. Replaced the battery and started right up.
BINGO !!!
You got it!
I remembered that 2 years ago that happened to my 1800 Goldwing.
Too bad as the battery was only a year and a half old.
Sure glad that was all it was.
Thanks to all. CK