Headlight blinks on and off...?

I rigged up headlights on both my 2 cycle bikes today, running them off the engine white wire. The Both work fine in terms of brightness, but both blink on and off. What's with that? It isn't a loose connection with either one, it is very regular...on for one second and off for one second, etc. Both lights ground to the bike for the second "wire"... is that what's wrong? In each case it is a six volt incandescent flashlight bulb. I had mostly wanted to make my self visible to others which this certainly does, but it also makes it pretty useless as a way for me to see. Any help is much appreciated.
Silverbear

Thanks for the tip. I'll give it a try tomorrow.
Silverbear

Well, I tired running a ground wire from engine to frame and still had a blinking headlight. I dug through the waste can to find the card the pair of bulbs came with and sure enough in small print is says, blinking bulbs. I guess these would be good for some kind of turn signals, but not a headlight, for sure. Thanks for the tips, both of you. I think a new set of bulbs will fix the problem.
Silverbear