Topic: cb400f wiring question

[kyre]

I've got a US 1975 CB400F with a wiring question for the HL power (if I get terminology wrong I apologize). I eliminated the starter and stock switch and have a question regarding power to the headlight. If you look at the first diagram, the BK/Y wire connects to the headlight switch (low beam/high beam only, no off) but once it goes through the fuse box, the BK/R wire "used" to go to the starter to deactivate the HL when pressed. I don't have that start switch anymore.




My question is this, Does it make sense to splice the BK/R wire into the BR/W for the taillight? My thinking would be the headlight will get power from the taillight wire once the ignition is turned on.




or....



Could I hook up the BK/Y directly to the brown? man this is the only area in my entire build I'm confused about, so far... any help appreciated.

If you need more info please let me know!

[thirsty 1]

Head light draw is 50w/35w. so 50w on hight beam is 4.16 amps and 35w on low is 2.9 1amps. The tail light circuit is drawing 2.25 amps with the brake light on and .6667 while running down the road (27/8 watt bulb). 4.16 + 2.25 is 6.41 amps drawn in the tail circuit with the high beam on and the brake light on. 3.56 amps with the low beam on and the tail light running as you would going down the road. Now the HL circuit and TL circuit both have 7 amp fuses so could you connect the head light into the tail light circuit for power? Yes but it's getting close to blowing that fuse.

How are you starting your bike?

[kyre]

Thanks thirsty1. I forgot to mention the tail light will be LED but the headlight is stock. I don't want to cut it close so I'm just wondering where I should hook up the BK/R wire for the HL power? Could I just splice into the red wire? Other options?

[thirsty 1]

At this point I'm guessing your harness is not stock LOL. Hang on a minute I just woke up and need to make some more coffee. Ya you could splice to the red but if all you did was take the switch out (I assume to clean up the bars) then why don't you just connect bk/R to Bk? The light will stay on while you crank but that's ok.  Since Y/R is the coil circuit don't hook onto that because your starter will run all the time. Does that make sense.

Just don't cut any green wires you bike will self destruct!

[kyre]

No electric start anymore, kick only so the Y/R wire and starter solenoid are long gone.  Yes the stock harness was modified before I bought the bike over 8 years ago, now that I rebuilt the bike
completely and am cleaning up the bars this is the one area I'm unsure of. If green is ground what is black? Is it powered? What would the difference be if I hooked the BK/R wire to Black rather than Red. Or vice versa? I sort of figured the headlight will be on when I kick it since my new handlebar switch only has a low/high beam switch and no way to turn the headlight off completely. Which I'm fine with since I always ride with the headlight on anyways. 

[thirsty 1]

Bk/R comes from the 7A fuse and turns into BK which then goes to a junction. This junction powers a few lights and switches so, yes, I would say BK is B+. So with the switch missing from the handle bars you should have bk/r and bk wires hanging freely. connect those together. I AN NOT RESPONSIBLE FOR SHORTING OUT YOUR BIKES WIRING. According to the diagram this powers alot of switches and lights and is the main power sorce.  My advise would be to get out a multimeter and check powers and grounds. If you dont have a meter buy a hand full of 7amp fuses.

I have stuff to do so I gotta roll. I'll check back later
Cheers dude

[kyre]

Thanks man, hooking to black makes sense.  I forgot black on these bikes are hot when ignition is on.  I'll get to the wiring again this week sometime and will let you know how it goes.  Had too many other things to do to the bike today.  Spring is here and I need my bike on the road again!

[bjbuchanan]

Hook up to the black wiring that is switched hot. Black/red is the headlight power that came through your starter switch. Your starter switch is a special dpst switch. Douple pole single throw. When just sitting there the black wire powers the black red which in turn send power to the headlight. When depressed on your bike, in the past, black diverted to the signal wire y/r for the starter relay, getting it?

Black power to the B/R would be the stock way of hooking it up. If you are doing your own thing I would just simply run black power to your headlight. What I would suggest and do on my bike for tuning is hardwire a toggle or rocker switch to the back of the headlight bucket to turn headlight on/off

It would save precious juice for a small bike to start up, and flip it when you need it


Oldmanhonda.com

I'm guessing you have a brown/red wire that goes from headlight fuse to bucket, to headlight on/off switch. Use that as your headlight power, with the rocker switch inline. That is how I did it on my custom harness

[kyre]

The inline switch on the bucket is a great idea to save juice when starting!  All makes perfect sense now. Thanks guys.

[thirsty 1]

Make sure you buy a switch rated for 10 amps. They even come in "cool" colors when switch to the "on" position.
Cheers

[kyre]

Thanks again guys. I bought a 15 amp toggle switch from McMaster Carr and finished the wiring today. Hooked the battery up and voila everything works perfect.  Love the headlight bucket main on/off switch for the headlight. Great idea. 

[thirsty 1]

That'll do it! Your welcome glad I could help.
Cheers man