Main point here is for Skip, the rattle you're are hearing is probably normal. It goes way when you increase RPMs, when you let out the clutch, and when you turn on your Hella lights.
Originally Posted by CARNEYM
Alternator, I know this because when I turn on and off my Hella lights, the rattle changes.
What was that proverb about the blind men and the elephant? They guy holding the tail says an elephant is like a rope, and the guy feeling the leg says an elephant is like a tree.
Any alternator that is rattling probably isn't long for this world. Two bearings, stator, rotor, field coils, diodes... none of that should rattle. However the drive train that powers the alternator could make noise. Hmmm, power is coming from the engine drive train, so increased load on the alternator (e.g. Hella lights) puts more load on the engine drive train and quiets the rattle. The rattle occurs at low engine RPMs and under no load conditons. So that's why people think the alternator rattles; the rattle ceases when the alternator is loaded. Actually what you are quieting is drive train noise.
That's my theory, and I'm still sticking too it.
And it is an annoying rattle, my bike sound like a shaking metal pail full of rocks when idling.