Headlight problem.

14 replies to this topic
  • dezdog

Posted January 03, 2010 - 11:36 AM


I pulled my headlight and tail light off of my 05 wr 450 a couple of years ago. I went to hook up the headlight a while ago and after starting it, the bulb got super bright and blew out. I bought another bulb and the same thing happened. I talked to a guy at the Yamaha dealer and he said it might be happening because the rear tail light is not connected. He thinks that it might need to be a fully connected circle (but wasn't sure). Does this sound true? Electrical is not my thing!!!! If this is true, is there an after market rear fender/light that isn't as huge as the OEM version. I like the new wr tail light, but I don't think they will fit.


Posted January 03, 2010 - 05:33 PM


I can't imagine how it would be related to the tail light. Almost sounds as if the voltage regulator is not doing it's thing or was somehow bypassed. Was the bike idling the whole time this happened or was it during reving?

  • drz=fun

Posted January 03, 2010 - 11:25 PM


I would be looking at the rectifier/regulator for a start.

  • freerider_australia

Posted January 04, 2010 - 03:19 AM


i have had the same problem the regulator is faulty it will still charge the battery as there is a seprate regulator with in the one unit

  • dezdog

Posted January 04, 2010 - 06:30 PM


I just started the bike with the button and no rev of the engine and the light went brighter and brighter and then blew out. I'll try the replacing the regulator. Thanks a lot!

  • klossWR450

Posted January 05, 2010 - 03:08 AM


+1 on the regulator, it should cut the charging voltage to about 14.5V, best check V on battery terminals with the engine runing/revving, you might see 20 V possibly

  • desertdragon609

Posted January 06, 2010 - 07:01 AM


check all your grounds before you drop cash on a new regulator! If you do need one, scope it out on ebay, don't pay 80 somethin retail for it!

Also check the resistance coming from your lighting coil..

Had this same issue on my 03wr250...was a huge headache.

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  • dustin63933

Posted January 06, 2010 - 12:14 PM


From what I've heard as a myth that some bulbs will blow if you touch them. The oil from your fingerprints heats up the bulbs and makes it blow. Maybe try not to touch them next time? This is probably common knowledge about being able to touch or not to touch the bulbs. But it might help. Might.

  • dustin63933

Posted January 06, 2010 - 12:14 PM


So maybe clean one you with some rubbing alcohol and some cotton or towel or something to thoroughly clean it up.

  • mikestator

Posted January 06, 2010 - 12:56 PM


Check the voltage at the headlight socket, if it exceeds 16 volts the r/r is bad. This will be AC volts when you are checking it.

  • freerider_australia

Posted January 06, 2010 - 10:24 PM


if you get a new regulator make sure that the head light is on all the time this will put less stress on regulator these are very crude regulators but do the job

  • Navaho6

Posted January 27, 2010 - 04:46 PM


My headlight went out last weekend. Battery also went dead during a ride (would not turn the starter over). I got a new battery and hooked it up today. Did some testing with a good (professional grade) multi-tester, and all is good. Cheap multi-tester was giving me poor readings.

Edited by Navaho6, January 30, 2010 - 01:45 PM.

  • Superboar

Posted January 27, 2010 - 10:59 PM


The WR450F 2003 model has two coils on the stator, one goes directly to the headlight and taillight as AC. The other coil goes to the RR and comes out DC which powers the starter motor and charging system.

In the AC circuit that drives the headlight directly, is a wire (yellow) that taps off that circuit and goes into the RR. Electrical gurus tell me that they cannot see how the AC circuit is regulated by this wire. Their guess is that this wire goes into the RR in order to catch half the AC sine wave to supplement the anemic charging system.

The unregulated AC circuit needs the taillight as part of the load - without the taillight, the headlight gets too much juice and blows.

I am having the same problem (blowing headlight bulbs) with a Baja kit which took the tail light out of the AC circuit and moved it to the DC circuit - probably because most DOTs require the taillight to work off the battery (DC circuit).

If somebody knows how the RR works on the AC circuit or knows the internal structure of the RR, please post an explanation.


Posted January 28, 2010 - 09:41 AM


Hmmm, I'm not sure about the '03's, but the '07 and up has the tailight as dc (runs off the battery when the bike is off). If I had this problem, I would probably look into running everything DC and using a trailtech or Baja Designs regulator/rectifier. To do the DC conversion at the stator you can either use the Baja Designs instructions off their website or purchase a higher power stator from Trailtech or Electrosport also has a new one out now. The benefit is you'll also be able to run hid if you like and enjoy 3 times the light for the same input.

  • phynx

Posted February 03, 2010 - 10:04 PM


check all your grounds before you drop cash on a new regulator! If you do need one, scope it out on ebay, don't pay 80 somethin retail for it!

I have one if that is what you need one cheap. Off a 2004 it that fits.


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