front and rear bulbs blowing

[doctorchopper]

I have an electrical problem, after about 15 min of riding or so my front and back bulbs blow. Any ideas, i was thinking voltage regulator? Shouldn't be a short as i don't think it would blow the bulbs just the fuse. I find it strange that both bulbs will blow at the same time. I tested the voltage at the battery and it varies from 13-14 volts with rpm so this seems normal to me but am unable to test it while riding for obvious resons

[Alternative]

You're right, the regulator is toast. The headlight and taillight run on AC independent of the battery, so testing the voltage there isn't much help. Try testing the voltage at the actual bulb plug, you'll probably find it'll go way over 12VAC when you rev the engine.

[doctorchopper]

thats right, i am getting up to 30 vac at the bulb, nice and bright for few seconds:mad: then pop.

[William1]

Bad gound can also do this.