Hi Fellas, i am still having an issue with my lighting on this bike. i have fully restored it recently and everything works fine except the head light is destroying bulbs very quickly. i fitted a voltage regulator inside the headlight bowl but the problem persists. with the engine not running the voltage at the battery is around 6.1 v, when i have it running the voltage at the battery is around 5.9 v. would this suggest that the charge circuit is not working ie bad rectifier ? is there a way to test the rectifier ?  . any thoughts would be great. thanks . 

A digital multimeter can test the rectifier. It should read a certain amount of ohms in one direction and none in the other. The factory service manual should provide the specs.

Yes as PAHIKER says above, check the rectifier for sure, & i know i test it wrong as only check to find continuity one way & none the other. So must wake my ideas up.
Have had the odd faulty ones where one terminal had corroded & broken off, & had another bulging out the side.
But talking regulator, if wired correctly it should save the headlight no mater what & even with battery removed or rectifier disconnected.
Also just thinking, inside the headlight shell isn't a good place for the regulator as absorb a lot of heat to send to ground--i think?

thanks for the replies fellas. does anyone know where this regulator should be fitted and how it connects into the wiring system on these bikes ? cheers.

Below is the m5-084 service bulletin for the regulator, they recommend mounting it to the headlight shell, but others have noted it should be grounded to the frame. 

www.yamaha-enduros.com/index.php/service...e-voltage-regulators

In order to splice it into the blue from the tacho or speedo illumination lights, some of us have made our own pigtail:-

Double female bullet at one end.
Single male bullet at the other.
Remove the wire with the single male bullet that comes from the tacho or speedo (doesn't matter which) from the existing double blue female connector and replace with the single male wire from the pigtail.
Fit the single male wire that you removed from the existing double female into the double female on the pigtail.
Fit the single male from the voltage regulator into the double female on the pigtail.

I fitted my regulator on to one of the horn mounting bolts.

Hi Mark, thanks for that detailed reply. i made an L shape bracket and fitted it inside the headlight bowl as far back as i can get it with an earth wire into the black at the loom and the yellow wire from the regulator spliced into the speedo connector it works great. you can instantly see the difference. thanks for your help. could you send a pic of the stand spring set up to my e mail This email address is being protected from spambots. You need JavaScript enabled to view it. as this is the last bit that i have to do . many thanks for your help. regards. Jez..

Small point, but if Yamaha say to mount it to the headlight Shell they probably mean on the outside so it gets forced air cooling while riding. It'll work wherever you mount it so long as it's grounded or if it has a ground wire to the loom the body won't need grounding. Some had them under the air box on plastic on Dt250's I think which isn't ideal for getting covered in dirt but it worked as had the black earth wire. Just check after a hard out ride that heat in the light she'll isn't causing a potential problem.