2tyam27

Thanks for the info, Speedshop. I have been working a lot lately so I have not had a chance to work on it further. The wires coming from my lighting coil are green, green with a red stripe and yellow. Which one of my wires would be the blue wire and which one would be the green wire in your diagram? Would my remaining wire go to the red pin in your diagram? Thanks again!

I had noticed for a long time that smoke appeared to come out of the head gasket when I reved the engine high. I always figured that it was coming from the exhaust and just looked like it was coming from the head gasket. I took a closer look when it was making noises the other day and decided that it was coming from the head gasket. I found a few of the head bolts loose. I pulled the head off and rotated the piston trying to make sure there was no play in the rod bearings. Everything looked great so I do not think the noise is evidence of a problem with the rotating assembly. I sprayed the copper gasket with "Copper Spray a Gasket" and put it all back together. I do not notice any noises now, but it still puffs smoke out of the head gasket when reved high. The gasket was used when I originally built the bike. I guess I will break down and pay the $45 for a new one and try that. The bike has never ran right at high RPM. It acts as if it is loading up. Maybe the head gasket is the culprit of that problem as well. My MX250 used to do the same thing, but replacing the stock blown out pickel silencer with a modern one fixed it. I guess it needed the back pressure. My MX400 has a modified CR500 silencer on it so I wouldn't think that would be the problem.

Does a capacitor keep the brightness of the lights from fluctuating with the engine RPM? Thanks for the link! It is my understanding that a bicycle horn mounted on the handlebar will work for inspection purposes. The last time I raced this bike, the top end developed a noise. It seemed to get worse when I was testing the magneto the other day. I guess I will pull the head and cylinder off and have a look.

Thanks for the replies guys. DirtyDT, do I have to run a capacitor if I do not run a battery? I found this basic schematic that might help me out. http://cycles.evanfell.com/wp-content/uploads/2010/03/Custom_Motorcycle_Wiring_Diagram_no_battery_by_Evan_Fell.png Speedshop, can you explain the center tap further for me? I checked out your website and it is great to know there is someone out there providing the parts to keep these things going. Do you know how much you will be charging for the stator kit when it becomes available?

Hello everyone! First, a little background. I have quit a few old Yamahas in my garage. I currently race a 75 MX400 and have many parts to these bikes. I definitely have enough parts to build another one. Maybe even two more. I have had the desire to turn a 75 MX400 into a street legal supermotard for a while now. I believe all the obstacles are easy to overcome, but electrical has always been my weakness. Since motocross bikes are all I have ever had, there has never been a need to know very much about the electrical systems. My vision for this bike is for it to look as close to a motocross bike as possible with the exception of the supermotard wheels. I do not want to run a battery. I want to hide the headlight behind the number plate somehow. Maybe I can use some mesh screening on half of the number plate so that the light will shine through the number plate. However, I have not had any luck finding a small enough light that fits behind the numberplate and has a high and low beam. My number plate is a DC plastics number plate so I do have more rom than an original number plate. I am wondering if I could use two small driving lights like you see at the auto parts store and just have them both on for high beam and one on for low beam? I would also like for the taillight/brakelight to not be so noticeable. I have seen those flexible LED lights and wonder if I could cut a window in the rear frame hoop and have the light shine through the window, or through the slit if you will? This may not be feasible though. Maybe I could use one strip of LEDs for the running light and have both strips come on for the brakelight? In Texas, I believe all I need is a headlight, taillight, brakelight, license plate light and maybe a high beam indicator. One thing I am not sure about is if the lights have to function with the engine off. If so, that would really cause problems because I do not even have room for a battery. If that is a requirement, I bet I could still get it inspected. A bicycle horn mounted on the handlebar will suffice for a horn for inspection purposes. So I am hoping the only thing that would take away from the motocross look is the license plate. Wiring up a system that would accomplish all of this is where I need some help. I have done research here and there and learned a lot, but am still not sure how to go about it. I have learned a lot from Neo's thread From my research, it appears that my original magneto would not run the lights. However, I have a complete electrical system to a 74 DT360 enduro including the magneto. Here is a picture of the two magnetos off of the bike. The one on the left is the DT360 and the one on the right is the original MX400. You will notice that the DT360 has the extra plug for the lighting. I tried bolting the DT360 magneto up to my MX400 yesterday since the DT360 magneto has the lighting coil, and it appears to be working great. It plugged right into the MX400 wiring harness (wires are longer than the MX400 though) and it fired right up. The DT360 had an extra plug for the lighting system which I obviously was not able to plug in. Here is a close up picture of the extra plug. The DT360 magneto is not the best looking piece as the DT360 was full of water and frozen solid, but appears to be functioning as it should. There are three wires going to the extra lighting plug. There is a green wire, a green wire with a red stripe and a yellow wire. I tested the AC voltage for each wire at idle and reving the engine. The green wire ranged from 35 - 100 volts, the green wire with the red stripe ranged from 17 - 60 volts and the yellow wire ranged from 11 - 40 volts. I assume this is all correct. A wiring diagram I have shows the green wire as the Daytime charging circuit, the green wire with the red stripe as the Night time charging circuit and the yellow wire is listed as the rear brake stop light circuit and the headlight main circuit. Since I do not want to run a battery, I assume the yellow wire would be all I need. Or, should I use the green wire since it is creating the most voltage and the regulator would clip the voltage to 12 volts anyway? I have the complete wiring harness for the DT360, but I wonder if it would be easier to make one from scratch since I want a much more basic system? Building a wiring harness from scratch is where I do not know where to start. Of course, I would not know where to start to modify the original DT360 harness either. I am thinking all I need is the SH-570 regulator/rectifier mentioned in Neo's thread. Would that be correct? I would like to run the original DT360 ignition switch (key), but probably get an aftermarket headlight switch. The DT360 has four wires, but the switch only has a on and off position. I would think with only having an on and off position, it would only need two wires? Would the regulator/rectifier be hooked up between the ignition switch and the magneto? Do I need the rectifier? If someone could give me an idea of how to wire this it would be greatly appreciated. I am sure I will have many more questions, but this is more than enough for now. Thanks ahead for any advice you can give. Any ideas would also be appreciated.

I will try to post up more information, and the questions I have, in the appropriate place later today.

Hi everyone! I am joining the forum in hopes of receiving some help with building an electrical system. I am wanting to take a 75 MX400 and turn it into a supermotard. As far as electrical goes, all I want is the bare minimum to pass inspection. In Texas, I think this would be a headlight, taillight, brakelight and maybe a high beam indicator. I have had this project in mind for several years. While doing some research, I came across Neo's thread on coverting his DT to 12V and figured I would join. Electrical is certainly my weakest area.