Topic: cb750K1 headlight not working - two tired ?

[newcbguy]

I have been struggling with the headlight on my recent build. I have a K1 which has a headlight on/off switch   on the RIGHT hand control and the hi/low switch on the LEFT side. My problem is that I get no power on the brown/white wire (headlight circuit). A) is there supposed to be power to this circuit from the ignition switch? -maybe a jumper from black to brown/white? (mine does not have this) its a NOS round plug ignition switch. B) Also I have a brown/white wire coming from the RIGHT (on/off) headlight switch, (which is not shown on the wiring diagram). How does a switch work with only 1 wire I have checked continuity from the brown/white RIGHT control to the other wires from that same control and dont get anything across any of the other wires. Maybe I rebuilt the switch wrong? Any ideas of what to check? Also if someone could give me the path of electricity for this circuit, for example starts at the ignition, goes to left switch then right switch. etc.  I have tried everything I can think of, but can only get the rear park light and gauge back lighting to work.

-confused in texas

[newcbguy]

anyone have any input on this?

[Kevin D]

Looks like brown/white is the gauge lamps/tailight, not the headlight circuit.
Black is the +12 volts out of the ignition switch.
Black switched to blue for hi-beam.
Black switched to white for lo-beam.
Black switched to brown/white for gauge lights/taillight.

Sounds like your switches aren't K1. What are the colors on the on/off switch and the hi/lo switch? Is the harness a K1 harness?

http://oldmanhonda.com/MC/wiring750K1.html

[newcbguy]

Kevin,

thanks for the reply. I went out and wrote down the wire colors I have.

Left switch:

Dark blue, brown/blue, brown/red,
white, gray, blue/white, light green, orange,
orange,white, blue, brown/white.

Right switch:

brown/white, black, black, black/white, green/red, yellow/red

As far as I know the wiring harness I have is from a K2 model, and
so far I have tried tying all the brown/white together and got nothing. then I tied the brown/white with the brown on the main harness and tied that to a black and got my tail light to work, but no headlight.  Should the brown/white wire get power at the ignition switch? How does the headlight get power? 

thanks!

[Kevin D]

 12 wires on the left! Yipes! Switches clearly not K1.

Do you have/can you use a meter? Sears has one in the Christmas specials for $10 or $20.

If this is your first visit into the headlamp shell you should know that by matching the wire colors together from the various harnesses, your bike will be wired correctly.
Jonesy has posted a list of wiring use by color code in the electrical FAQ. It will help you to find what they all do. I don't think the color codes changed over time, but you have some color combos there not in the K1 drawing. Check this out:
http://forums.sohc4.net/index.php?topic=1012.0
Looks like the brown/red is the fused headlamp power.

Got a clutch start switch on the left side switch?
What are the colors on your headlamp plug?
How many fuses in the fusebox?

[newcbguy]

Kevin,

I have no idea what a clutch start switch is, but I dont have to do anything special to start the bike. It will start without holding the clutch in. The stock harness was trashed so I replaced with what I believe to be a '72 harness. I only have 1 fuse that is between the red from ignition and battery. The left switch has a horn, headlight hi/low and turn switch. the right has on/off which I believe to be the headlight on/off switch and the start button and kill switch.  I dont know where the brown/red wire would hook to? Does the black wire at the right control give the headlight/ park light circuit power when the switch is in the on position? I think I need to take apart the switch if this is correct because I cant get continuity between the brown/white and any other wire on the right switch. I may have put it back together wrong.

thanks again!

[750essess]

Power should come in to the right headlight on/off switch with the black wire and go out with the brown/white to the left brown/ white high low and out to the headlight through the blue and white wires. Confirm the wire colors by using a meter to test witch switch does what.

[newcbguy]

thanks for the reply, it makes sense that the power should come into and out of the on/off switch first. I am really confused about the controls now because I have a factory throttle stop on the right switch. which is only supposed to be on ko/k1 bikes. Maybe the left control switch was replaced at some point, because it appears to have wiring like the later ones. My switch must not be working correctly Also in the link that Kevin posted, it mentions that the start switch interrupts the headlight circuit, and can be the reason why the headlight doesn't work. When I check across the brown/white and the 2 black wires on the right switch with my meter I don't get anything when turning the switch on/off.

[750essess]

You could eliminate the on/off switch and run a black to the left switch to get it running temporarily. Then the headlight would always be on when the ignition switch is on. I wouldn't think it would have a headlight interrupt with the start button cause it has an off switch, that was usually done on later models that the headlight was always on.

[newcbguy]

thats where it gets confusing, I believe over the weekend while I was trying to figure this mess out, I did try to hook the left switch brown/white to one of the black hot wires from the main harness, but still got nothing. Thats when I came to the boards to get some facts straight. Maybe both of my switches are fubared?  The only thing I didnt try was hooking the black directly to the white or blue, but I did verify that the headlight worked by hooking it to an external battery. -been fooled by that before!

[750essess]

Does you meter have a beep or ohms setting, use it to test the switches. Sounds like your getting it narrowed down. Dont for get to check the ground to the headlight also.

[newcbguy]

Well, I took the right switch apart tonight and it was indeed assembled wrong. I fixed it after dropping the little ball bearing that goes in there about 10 times and a few bad words. Long story short It works! I even went as far as to wire the signals too!  I just went for a very chilly ride to try out the light even!  Thanks again for the help guys!

[Kevin D]

Persistence pays off!!

Looks like your handlebar switches are close to K3-K7, although I counted 11 wires for the L/H switch there.
http://oldmanhonda.com/MC/WiringDiagrams/MCwiring.php

My help runs out pretty quick if its not a K1, and even then it's nothing to write home about.

Sounds like you enjoyed your ride - none of that here until a lot of snow melts.