price81

This was my first thought as well however, I believe that only in models after the DT100's are there voltage regulators....any other suggestions?

I have a 1980 Enduro DT100. Recently, the old sealed beam headlamp burnt out so I replaced it with another 6V 5 3/4 inch bulb. They were the exact same type so I figured to have no problems. After 3 days of driving it (only in the daytime), I noticed that both the high and low beams were burnt out. I didn't notice this earlier because I hadn't driven at night. The output from the battery and headlamp plug while running is about 18 volts.......any clue why? When the engine is off, the old battery reads 3V. Is there any chance a spike caused this burn out of both high and low beams? What should I do before I put in another new sealed beam? Help, please!