Vintage Dirt Bike Q & A

I have a 75 MT250 that is nearly road-ready again, but I need lights at the back. The taillight and brake light don't work, and the turn signals are missing. I would like to do a license plate mount with a red strip along the top for the tail/stop, and yellow down the sides for the turn signals, but for now I haven't been able to find any 6v LED stuff. Will 12v stuff work, or am I looking at making my own LED boards? The bike had a burned out 1157 bulb in the taillight housing, I replaced it but the light doesn't work. I do still need to put a battery in it, but the headlight still works on high beam.
Also, all the wiring diagrams I have found are pretty vague, does anyone have some real wiring diagrams with wires colors and connector locations?
Where can I find a replacement headlight bulb for this bike?

I seem to have posted a little prematurely on this. I went and messed with the wiring a little, and found one of the green wires at the taillight unplugged. Plugged it in, and now the brake light works. Still no taillight though, so I'll have to test that a bit. I also found three wires just dangling under the tank, I'm assuming this is where the "winker relay" is supposed to live, but there's three wires. Everything I've found says a two prong relay is used, so I'm not totally clear on how this is supposed to be wired.

There is a service manual for the 74 MT250 in the "manuals" section of this website. That may be of help to you. It has a wiring diagram. Maybe you have seen it already.

I have downloaded and studied the diagram, but it's not the clearest scan and what it says doesn't always mesh up with what's on the bike. Whether that's manufacturing variance or just this bike having been messed with over the years I don't know, but that makes it a bit difficult to get to the bottom of this whole thing. As an example, that diagram shows two greens and a brown to the relay, where there's two browns and a green here, it also shows one green not connected.
I'm going to go have the diagram printed tomorrow (I don't have a printer since I am in the midst of a 850 mile move), and see if that makes it a bit easier to study.
Aside from the electrical stuff, this bike runs great now that the crankcase is properly sealed. Plenty of power, and a really mean sound make it a bit of a head-turner too. I'm hoping to ride it a a commuter starting in a week or so.

The green wire is not used on the "winker relay" the "G" in the wiring diagram stands for Green. the "Gr" stands for gray, and the "Bk" stands for black, look at the wire colors closely. I recently purchased a new winker relay from Bike Bandit for my MT just a few weeks ago, They carry quite a few parts for the MT. I have purchased numerous items from them for mine. The website is www.bikebandit.com. Go to OEM parts and input the year, make, and model of your bike, it will bring up every part associated with it. They don't have all parts, but a lot of the small stuff that might be needed. I just got fork seals, levers, numerous screws and fasteners, new rubber for the pegs and kick start just to name a few. And on the rear tail light, and this might be a "Duh" moment, try replacing the bulb and make sure there is not a lot of rust inside the socket where contact points of the bulb might be. Make sure it's the right bulb as well, that takes a "1154" bulb. Hope this helps ya out some.

Andy

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Ok, I have this all fixed now for the most part. It was a bit difficult to sort out since the lighting isn't done off the battery but off it's own a/c coil.
I found that the solder joints in the high/low switch were broken, which is why I only occasionally had light. The on/off switch had some corrosion, so once that was cleaned I had taillight power. I spent an extra hour or so diagnosing the lack of rear light problem, traced power all the way to the socket, and found that the new bulb was burned out. Apparently, without the headlight the voltage goes pretty high there.
For the time being, the output of the headlamp switch is just plugged into the low beam side of the headlight, giving me a constant light with the engine running. Once I have access to all my tools again, I'll resolder the joints and get the high/low working properly.
The stock style rear turn signals are difficult to find, and prone to being ripped off, so I adapted a different setup:

It's off a slightly newer road bike, but all the wiring just plugged in and worked. It also stiffened up the already damaged rear fender.