Matt Hotch Designs is working with a company to develop a new motorcycle battery. They are a Lithium-ion Polymer battery which can be built in a variety of configurations with the leads positioned wherever they are needed. They weigh about one quarter of the weight of a conventional battery, but what makes these different is what they can do.
There is a video on their website that shows Matt Hotch running a test on a custom V-twin with a 113 inch engine. He pulls the plug wires and begins to crank. After one minute and 45 seconds the battery is still cranking fine but the starter is smoking so he stops for about 30 seconds then cranks again for another minute or so until the starter begins smoking. He waits another 30 seconds and then cranks until it finally quits, at which time the starter is practically on fire and the rubber insulation has melted. Watch the video, these times are not exaggerated. This is a super battery.
Of course batteries like this are not cheap, we're talking many hundreds of dollars but for high end customs or any other high end bikes, these might be worth looking into.