Mysterious headlight problem

My mates headlight keeps turning itself on / off as he's riding along. We've checked all connections and they all seem good however when we touched both contacts on the bulb with a multimeter the bulb lit up. This is with the bike running and the bulb connected with low beam on. Could this be a short within the bulb itself?

He's riding a YBR 125 with the single headlight.

[tigersaw]

Is it supposed to be on all the time, so the fault is that it has become intermittent?
If thats the case it sounds like bad joints on the lampholder from fatigue or corrosion.

Cant rule out a bad bulb, but it would have likely completely failed after a while and your test indicates connections, just from the pressure you applied with the leads

Yes the headlight is meant to come on automatically but it doesn't come on until a good 3 seconds or so after the bike has started.

I'll take another look next time I see him.

Thanks