the batteries i was talking about were interstate rated at 310/320 cca and, come to find out, all they were was re-badged 270 cca yuasa brand. no improvement from the original, just lied to about the cca. my suggestion is to go with the best you can afford, whether it be H-D, Braille (what I have), Big Boar, or even one of the new lithium-ion ($$$$$). just research and make sure of what you are getting.
not on a bike, but in the past, i have had the experience of corrosion building up INSIDE the insulation of the battery cables where it was not visible. everything looked good but i could not find the source of my problem, until i tried flexing the cables from one end to the other and found a hard/stiff spot. ohm out your cables/wires and see what they read. should be -0-.