The light will run on AC, bulbs don't care they are just a resistor that glows... LOL
The problem is you will need to add some regulation. So if you don't want the electric start working again, and don't plan on using a battery anymore, the easiest way is to get a AC regulator and wire it to the stator output and wire the output of the new regulator to the headlight.
The electrical system is easy peasy on these though, stator output to rectifier/regulator, then the output of that to the battery. Battery voltage goes through the ignition switch to the headlight switch and to the lights. The most common problem i run across on the 200E is a bad rectifier/regulator. But make sure the stator output is good also. Get a voltmeter set to AC and put it across the yellow wires from the stator, start it and see what you have for output, it will vary with engine speed. If thats 10-20v at idle and goes up with engine speed you should be ok there. I say 10-20 at idle because depending on what your idle speed is set to and the health of the flywheel magnets and the stator coil it varies.
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1984 Honda ATC200ES "Big Red"
1982 ATC200E "Hondie"
1988 TRX300FW "Project Quad" Still in progress....