Topic: CB400f clutch switch wires

[goldwing55706]

A few years ago I purchased a 1975 CB400f through an online auction.  Now that I have my CB350f pretty well operational, I’m starting on the 400f.  The previous owner was obviously having wiring issues because all of the wires under the gas tank and all of the wires in the headlight bucket were disconnected.  I have reconnected most of the wires and studied wiring diagrams but have a question or two:
1.  The clutch switch wires are just hanging down from the handlebar.  Do these two wires (green and green with a red tracer) go into the headlight bucket?  I have not figured out where the green wire with the red tracer connects.
2.  Do the clutch wires need to be correctly connected to get spark?
Thanks for your help.
Jon

[mwvachon]

Um... I don't think there are any clutch switch wires... Perhaps you meant the front brake switch?

[goldwing55706]

Thanks for the reply.  I did mean the “clutch switch” Honda part #35360341000. 

[mwvachon]

Well look at that! Didn't realize this model had this. Guess I need to check on mine!

[mwvachon]

Yup, guess I have one as well on my '75 CB400F. Here is a schematic that may help(?)
http://manuals.sohc4.net/cb400/technical_reference/WD40075.jpg

[Kevin D]

Goldwing, I have no particular knowledge of CB400s, but I have been studying the various wiring diagrams while trying to help a guy in another thread.
 The clutch switch is in the starter magnetic switch control circuit = electric start doesn't work without clutch disengaged.
Older bikes don't have it, some consider it a nuisance and bypass it.
It's not part of the ignition circuit and looks like it plugs into the main harness.

MW you can type faster than me!

[jakec]

On my friend's 400 this part broke off at the clutch perch and it had no effect.

[Tim2005]

They plug in inside the headlamp bucket. Though it's pretty rare for it to be working or not bypassed anyway.

[Bodi]

It does not affect the spark. The switch just enables the electric starter when the clutch lever is pulled in. The neutral switch also does this, but through a diode.

[goldwing55706]

Thanks everyone!  I have the headlight out and do see two green with red tracer wires hooked together.  Maybe my clutch switch has been bypassed. I know that my electric starter works without the clutch pulled in.

[mwvachon]

I haven't messed with mine, but wondering out loud if the neutral lamp is also involved some how? Test would be to switch into gear and try starting with the clutch lever in the normal position and then pulled in (to contact the switch) Make sure the rear wheel is off the ground! (center stand)

[Bodi]

The clutch lever switch connects one solenoid relay control coil wire to ground directly, allowing it to work when the button is pressed sending battery power to the other coil wire. The neutral switch connects to ground in neutral, letting the neutral light go on. It also connects to the solenoid coil's wire through a diode (black thing near the regulator and flasher)... that diode just keeps the clutch switch from lighting the neutral light whenever the clutch is pulled in. It's a pretty useless neutral light if the diode fails short - you will always think it's in neutral when the clutch is disengaged and may be surprised if it isn't.

[goldwing55706]

Thanks everyone.  Today I took a fresh look at the CB400f and found the old green and green with red tracer wires still connected in the headlight shell encased in a plastic housing (the ends of the wires were cut off and didn’t stick out of the plastic housing).  Bottom line, I hooked up my clutch switch wires to the proper connections in the headlight shell.
Now to figure out why there is no spark.  Will check for power at the coils, power down to the points, coil primary and secondary resistance, point gap, timing, etc.
Thanks again,
Jon

[mwvachon]

Just one more...
Found this great diagram of just the starting circuit here:
http://manuals.sohc4.net/cb350/service_manual/SM350400_3.pdf
Take a look at figure 5.2. This gives a detail view of how the circuit is laid out.