Good information! I actually recently bumped my start button by accident and discovered I could modulate it. I don't suppose that would cause any problem to the bike, would it?
Most bikes use a small relay that disables the starter circuit whenever the alternator is putting out more than a certain voltage level - and that relay keeps the starter from being energized while the bike it running.
The issue is this: by using the starter button as a headlight modulator, you are putting A LOT more uses on that button than it was intended to experience and so the contacts inside may be taking a bit of a beating. Also - if that relay ever fails to operate, the starter will engage the running engine and it, or something within the engine such as the ring-gear on the clutch basket could be damaged - with expensive consequences.
I would urge you to use a proper modulator. They are not expensive, they are easy to install and they do not risk damaging anything.
Now, on the issue of modulators for LED lights - apparently, there
are modulators that work with LEDs.
It is just a question of tracking one of these models down and using it if you have swapped an LED headlight onto your bike.
