Currently working on the wiring harness for above mentioned bike. Question- if all wiring is connected correctly, will I have power to more than just the horn without the bike running. Have followed the wiring diagram for all circuits, everything looks good. One thing I did notice is that one black wire from cdi goes to coil, and the other goes to ground. Is this correct? The third wire (black and white) goes to kill switch. Any help would be greatly appreciated.

Black also goes to regulator and battery, the Black/white, goes to kill switch & ignition switch, and the black to coil
The turn signals & stop lamp should work without engine running, [ DT400B diagram]- CDI is No 7. Iggy No 18 Battery 28

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Would anyone have information as to where the voltage regulator was placed on the 76 dt400. I managed to find a new oem regulator for my 75 but really don't want to put it on back of headlight. Also would the wiring on the service bulletin still apply to the new location?

76 dt400 regulator is mounted on front air filter box- the 75 air box does not have mounting provision like the 76. Also the wiring harness for the 76 has an adapter location by the air box to plug it in. Best place to adapt the short lead off the regulator is on the back of the headlight. Pick up a yellow lead in the headlight bucket and you are done.

I mounted mine below the fuel tank just in front of the coil mount. I know the service bulletin recommends the back of the headlight, but it is a cleaner install down under the tank. Plenty of air for cooling there too.

The wire on the OEM reg is short, but you just need to make an extension lead to connect it up in the headlight. I would recommend connectors from VintageConnections.com too. They are essentially OEM style, size & quality.

Here are a couple photos of the 76 DT400 voltage regulator installed on the air filter enclosure.

thank you very much for the photos, they help tremendously! Should I still follow the wiring info on the service bulletin for the 75 as to where to connect in?

Please email me svc bulletin and I will look at it This email address is being protected from spambots. You need JavaScript enabled to view it. without svc bulletin- here are my thoughts-
The schematic above would lead me to believe it would be wired into the hi beam ckt. (Yellow wire) - the black wire on the 76 photo is just a bonding wire for ground - because the air box is isolated from frame ground by rubber dampeners. You might want to run a bonding wire inside the headlight bucket to the headlight bucket if you mount it on the headlight. Take a ring terminal with a jumper wire and mount it with the bolt that holds on regulator and connect other end to a black ground wire.- about a six inch piece of 16 gauge wire should work. If you mount directly on the frame the bonding wire should not be reqd.

Here is a link to the service bulletin:

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

AAAHH, makes sense now. This Service bulletin potentially saved me from some problems on my 75 DT400. I was cleaning up some jumpers in the headlight and now I know why they were there. I need to follow the service bulletin and connect the regulator closer to the power source to take care of all lights. I was going to connect it to the yellow wire but is says to connect it to the blue. Was working good before I started trying to clean up a few things. Brings up another question as to what wire the reg. is connected to on the 76 wiring harness. I would like to get my hands on a 76 DT400 wiring diagram.