CM400 headlight wiring?

[barelycompetent]

Hey all, so you guys and gals have helped me in the past so I figured I would ask the collective minds here and see if you had any ideas.  My 1981 CM400 that Im building has decided that the headlight should not work or come on.  I have checked the bulb and it appears to be good, the filament doesnt appear to be burned out in high or low.  I have not unplugged any of the wiring except for the turn signals, which I labeled so I wouldnt get them mixed up.  I had to disconnect all of the plugs so that I could swap out the headlight bucket, and I plugged everything back in the way it was.  Double checked that nothing was unplugged and it was all plugged in correctly, placed my headlight in and connected it, turned the key, got both turn signals on and working but my headlight wouldnt come on.  I started the bike, still nothing.  So I started tracking the wires down, and got to the fuse box, and heres where Im scratching my head on this.  In the fuse box the there are 3 fuses, the top is a 15amp main, the middle is a 7amp headlight and the bottom one is a 7amp taillight.  I turn the key on, take my test light and I get power on both sides of the main, power on both sides of the taillight, but nothing on the headlight.  I swapped the headlight fuse with the taillight fuse and its good.  Why would I get power at the main, and the taillight, but not at the headlight?  For the life of me I cant figure out if there is a short, where it is, or what is causing this to happen.  Any ideas?  As always any information is greatly appreciated.  Thanks in advance.

[TOOLS1]

The headlight circuit runs from the switch to the fuse, then to the starter button, then the dimmer switch, finally to the headlight. So I would be checking the ignition switch.
TOOLS

[barelycompetent]

I checked the switch at the back, I get power to my test light at all wires except for the green wire that comes off and the black with white stripe wire.  I put my test light on the positive side of the battery and checked all wires for ground and got nothing on any of them.  From my understanding the green wire is the ground for the bike, and I get nothing on that at the ignition switch.  My brake light and turn signals all come on though.  Which has me stumped.  If Im not getting a ground with my test light at the back of the switch, would anything else come on?  The tach and speedo lights come on and so does the neutral light and oil light, just not the headlight.  Does that sound like the switch then?

[Black 750K8]

First off you will not have power on the green wire that is ground. It works like tools said. I have never had a 400 so I can only tell you about the 750 but most of these old Hondas are wired close to the same. One thing tools did not refer to is on the later bikes the headlight will go through the start button so when you press the start the headlight goes out and when you let go it comes back on weather the bike starts or not so look at too.

[TOOLS1]

I did say that the circuit went through the "starter button".
TOOLS

[barelycompetent]

Well after sitting down and going through a wiring diagram, and looking at the only thing I had changed on the bike, and tracing the wires through I figured out what it was.  At the back of the bike the turn signals, and the brake light are all grounded inside the bracket on the rear fender.  I removed the rear fender and the factory turn signals and brake light, I unplugged all of those wires from the harness by the air box.  I had thought that the green wire was still grounded, but by removing the rear fender with all of the factory lights, I had also removed the ground on the fender.  If this makes sense, I had basicly removed a ground from the circuit.  After tracing the wires I found where the brake light ground meets with the headlight and goes to the ignition switch so it all tied in together. I wired a ground to the frame and now everything works as its supposed to.  I doubt Im explaining it correctly but it all makes sense in my head(which is a very scary place to go sometimes lol).  So thanks tools, and black750 I appreciate the responses!  All is as it should be now!

[walzi]

Could you go more into detail on how you traced the wire from the tail light to where the brake light ground meets the headlight? I have th esame issue.