Motorcycle Repair: Motor Cycle Headlight Blows, light bulbs, uncommon problem

Question
Sir,

I have Yamaha Junoon Euro-2 2012 model and it has a problem that at night time when driving the bike. its beam become bright suddenly and blows the beam.....I have checked it to Yamaha authorized mechanic and he just unplug the rectifier and again plugged in saying that it is the fault that the terminals were loose but now again it is doing the same as blowing the light and it has blown about 7 bulbs right now in 2 weeks

Please tell me its solution

Answer
Ali, This is not an uncommon problem. Test the voltage at the battery terminals with the bike off,it should have a little over 12 volts using a volt meter. Start the bike and test the voltage at the battery again while unit is idleing. It should not go over 12.9 volts. Now rev the engine up to about 2500 to 3000 rpm and test the voltage at the battery again. It should not go over 13.8 volts. If it does the voltage regulator may be bad  allowing it to overcharge the system, and blowing out the light bulbs. If this continues it can start taking out other components which can get expensive. If the tests show its overcharging the purchase a new voltage regulator,then retest the system again and see if this helps.