Totally not a major problem but I wonder sometimes

[mainlinecoffee]

Why does my idle drop when I turn on the headlight? Is it choking the sparkiler?

[Water Warrior 2]

The power is being divided between 2 systems and neither one receives as much power as they want. Also the charging system is not designed to make power at lower rpm's so you have a loose loose situation.

[mainlinecoffee]

Interesting. What are the two systems? I assume it runs more off the battery under 1200 rpm, seems to be the magic number on most bikes.

[alantf]

What year is your bike? On the ones from a few years past, up to the present, the headlight is on all the time, and cannot be turned off. So those of us with later bikes can't even do a check, to see if it happens to us. Can anyone out there with an older bike do a quick check, to see if it happens to them?

[tintankaussie]

Over here in aus land and my bike being a 1998 model,my head pight comes on as soon as i turn the key on.bike starts first time and i use a good quality battery,no dramas...ken

[raul10141964]

when the generator ned to put more output increase the drag on the engine

[jonathan180iq]

What are the two systems?

Engine is primary - lighting is secondary.

Sit on the bike facing a wall.
Turn it on.
When you rev past 2000rpms, the headlight will brighten.
This is also a poor-man's method for testing if you're stator is doing its job.

[5th_bike]

when the generator ned to put more output increase the drag on the engine
This is the correct answer. The engine has to do more work from the same amount of fuel. Hence it will run a bit slower.
Then it gets less fuel. It will run a bit slower. Etcetera, until a new balance between energy input and output is reached. At a slower rpm.