The bike isn't throwing away electricity. The load on the engine from the stator is the resistance of the system attached to it. As you draw more amps, the stator will be harder to turn, using more fuel.
I was basing my statement on a previous post, I don't know much about the differences between motorcycle equipment and automobile.
So it's the same as a car alternator, load increases based on power requirements. That would change things a lot. Electrical power generation isn't terribly efficient. part of the reason why I scratch my head when people say that electric cars are going to save the environment. You've got to produce the power (not terribly efficient, but can be clean), transmit the power (and transmission line capacities are based on their ability to dissipate heat before they melt, so there's a lot of heat being generated here), charge the batteries, then use that power through a control device into a motor. So 5-6 steps, each with an efficiency loss.