Problem with the head light

Most of the "white wire power" that these engine produce could barely light up a fire fly let alone a headlight. Your best bet is to run your headlight off of a battery pack.
The white wire is rated at 6 volts, 3 watts, 1/2 amp. Most seem to actually produce 6 volts, 1.5 watts, 1/5 amp.... if you are lucky.

You can buy this lighting coil from ebay 12 VOLTS MINI-GEN MAX For Motorized Bicycle Lighting | eBay

That is a good alternative too!
As for a battery, whatever fits the size you want and has the amp hours that meet your requirements.
You also could use the white wire or the aftermarket Mini-Gen Max to charge a battery for a system similar to what a motorcycle has. There are many threads on this subject too. Here is one that I found in a search of this site:
http://motorbicycling.com/f50/white-wire-charging-system-question-34240.html

And another: http://motorbicycling.com/f50/step-step-diy-rectifier-instructions-32246.html

3-LED Flashlight Replacement Bulb (6-Volt) - C. Crane Company (800) 522-8863


That would be perfect. LED's use a very small amount of current and even 1/5 amps from the white wire should be plenty. No gaurantees though that listing doesn't show how much power it draws but it should be fine.. You don't even need a case. If it were me I'd probably just solder the white wire to the tip part that is positive, then a negative to the screw part of the bulb thing. Then hot glue over it to add rigity and protect those parts from rain. Otherwise should be good to go I think.. That's my suggestion atleast.

Otherwise I'd buy a 7a/hr. 12volt battery. It's only 5 pounds. A ton of electronics use 12 volts and I'm sure you can find just about any good flashlight to run off of it.

Swap your generator over to the 12v setup like Max350 suggested and that should do the trick. Then be sure to run LED's for less power consumption.

I am using Normans Light Kit. I had some problems with the light killing the engine, till I found the right gap. Try filing your spark plug's spark arm down to a dull point (don't file the electrode!). Set the gap at .025" and see if it runs or kills bike when switched on. Also check your ground connection. How are you grounding the light? What kind of light or bulb is it? If it's a 12v bulb, your bike might not be making enough juice.

re: 12v SLA batteries. They can't be charged over 12v very successfully, and they drop rapidly when used at peak power. I have messed with them to run 12v 20w halogen light before. Run time is around 1 hr in weather above 50F .