Topic: CB400F Wiring Problem

[John V]

Hey guys,

I've done a bunch of searching here but have yet to come to a conclusion.

I have a '75 CB400F that I bought complete but not running. I understand the wiring for the RH controls differ from year to year. My bike has the right hand controls with a lights On/Off switch, the standard Off/Run/Off kill switch and a starter button. The starter button is the type that simply grounds the yellow/red wire, NOT the one that powers the starter relay and switches the headlight off when pushed. The wires coming from the RH controls are as follows:

Black (switched power to kill switch)
Black (switched power to headlight on/off switch)
Black/red (headlight on/off switch to headlight fuse)
Black/white (kill switch to coil power)
Yellow/Red (start button)
Brown / blue (no connection as far as I can tell)
Yellow (no connection as far as I can tell)
White (no connection as far as I can tell)

I cannot find a wiring diagram that matches this bike. The odd thing is that the other side of the starter relay circuit (green/red wire) is also not powered. It connects through the clutch switch to ground. Obviously, as a result the starter button does nothing, since it's connecting both sides of the solenoid to ground.

I'd like to make the wiring on this bike correct. My guess is that these RH controls are not from this motorcycle, maybe from an earlier CB? My LH controls do have the dimmer switch on them. Should my bike have a RH control with the switched-hot starter button and no headlight on/off switch? It seems that the answer is yes, but I'd like confirmation.

Thanks for any assistance.

[rockvegas400]

Hello John,

My bike is a 1975 Australian (U) model and has starter button, kill switch, and headlight switch. The wiring diagram I found matched it most closely was the UK model. The Brown/blue wire in the headlight switch heads to the taillight fuse.

I have attached Haynes diagrams for both UK and US models for your reference. Neither have a plain yellow, or white, wire included.

So you are perhaps correct in thinking that the control is from another bike. the Davis Silver UK site (and I assume the newer US one) has photos of controls for several year and country versions of the 400 if you want a visual check. Just search via model for the list of parts with photos.

Good luck with your project.

Justin

[John V]

Thanks for the reply. You're correct that the brown / blue went to the taillight fuse, I was wrong on that. I don't know what the purpose of the white or yellow wires are.

I believe I have it wired correctly now and everything works except the starter button. I'll source the correct RH controls and go from there. Thanks,

John

[bjbuchanan]

Does your yellow and white wires connect to your headlight slider? If so, your switches are from a cb360t, any of the smaller twin bikes really. The yellow or white, can't remember which, activates a second charging circuit on those bikes, it ramps up charging for the brights on that bike.

On your bike you can simply connect to the low beam wire (you can figure it out by manipulating the slider and seeing which wire is in contact on low) and connect that over to your LH switch for headlight power. Ignore the other wire

Try grounding your green/red wire on the solenoid, hotwire your solenoid. Does the E-start work now?

[John V]

The solenoid works correctly. If I apply 12V across it, the motor cranks.

The issue is that with the RH controls I have, there is no provision to wire hot to the start button. And the clutch switch and neutral switch are connected such that it's not practical to wire hot to that side either.

A new set of controls is in order, I just need to figure out where to get one that isn't purple!

[John V]

Ended up buying a replacement switch pod which was correct for the bike, then swapping the lavender kill knob for the original one on the incorrect switch. Once I got everything wired up, everything worked correctly. Thanks for the help in determining that I just had the wrong switch pod.