BigBlkYJ

I like that idea. I wonder if I can just find a conversion headlamp assembly that will accept cheaper bulbs but fit into the sealed beam shell. The sealed beam ones aren't too expensive. $10 each...

Well I'll have to see tomorrow they had to order my headlamp because I took the last one haha. The 6 volt lamp I'm testing with is only 17 watts also I'm assuming it will only get better with the correct 25 watt one in there. What seems so odd is that if any bulb blows, it could possibly take everything with it. (Whats funny is my manual actually says this in there after reading for a while, and also says that if a headlamp goes to try and idle it home basically)

Well i changed the front headlamp to a rigged up 6 volt lamp and also replaced the smaller meter lights, and the voltage seems to be better. I could not get over 8.5vac with all of them plugged in and working. Maybe you really do need everything hooked up and working for it to be correct...? I guess the battery must help regulate the AC somehow?

OK, quick update. The diode wire changes color after it leaves the diode just past a connector by the brake pedal. The wire color changed to Black/white stripe. I followed it back to the run/stop switch. So basically it goes from the engine stator harness to the run/stop switch (at least from what I can tell) and its spliced once with a barrel connector in the headlamp assembly. I should also note, that with my meter connected to the headlamp, the voltage is still almost 14vac when revved up. So I think the problem is still there! :(

No markings...What you see is what you get.

Well I'm going to play around with it this morning, I think what I'll do is plug my meter right into the lamp socket as before. This whole diode thing has me wondering why it's such a big secret, and not on any of the diagrams, or parts ordering pages. It's obviously a replaceable part since it's plugged into the harness and not hard-wired. As far as numbers on it, I didn't pull it completely out, for fear or damaging it to a point where it would not work at all, but I'm sure there are some on there. I've never seen and electrical component without them, and there doesn't appear to be enough colored banding to make sense of a value.

Well at any rate THE BATTERY FIXED IT. Apparently you must have a battery in the circuit to help regulate voltage. The minute I put it in there the voltage dropped down to around 6.5vdc at idle and just under 8vdc with it screamin. Mind you this is on the dc stuff like the tail lights, blinkers and horn. I have yet to get a new headlamp to test, but I'm assuming this has fixed the problem with it also.

I checked the rectifier also, checks good. The bulbs are all brand new (well they were last night, now they are junk) I'm going to pick up a battery for it right now, and we'll see if that helps. I'm not going to be doing any more tests with a new headlamp, as they are hard to find are sorta expensive to keep blowing up haha! Also, i have looked high and low, and there is no sign of a resistor. If there is one, i can't find it, and i'm not tearing the wire loom up to find it unless i know 110% there is one.

Ok, maybe these will help... The last one is of that diode connected in the bike.

You want a picture of the rectifier under the tank? I checked it with my meter but not the lamp test. I guess i could try that also. I just got off the phone with Yamaha customer support, and they confirmed the bike is a 74 DT175

Well there's definitely no heat here, since the entire thing was cased in a poured rubber of sorts (i'm going to just shrink tube it back). I guess its working normal though since it functions. I'm still wondering if my not having a battery in place is causing this issue. However I'd hate to fry a brand new battery if it's not.

No there is definitely a rectifier. Its mounted under the tank, and has an integrated heat-sink. What i found odd about that was the book said that the electricity should flow when connected from the pos. lead on my meter to the red lead on the rectifier. However its opposite. I would think though that this being from the factory would be correct. The leads are soldered onto it, not push on.

The engine # is 443-010XXX (do you need the entire #?)

Well i have a diode check on my meter and it only works in one direction with this thing. One way the forward voltage drop shows up as .53 volts. But just to be sure I did check it with a 6volt lamp, and it will only light in 1 direction.

The resistance was 166K ohms which seems pretty high to me. Also I don't know that this is actually a resistor. It acts like a diode when placed in diode check mode on a meter. Also its connected to the harness that comes out of the engine stator assembly's black wire (which has a double connector on the end, but only this is connected to it) The other end plugs into the harness that heads up into the main harness with the rear brake pedal switch.