Topic: 1977 CB400f headlight problem

[sepling]

My headlight doesn't work after working intermittently.  Am I correct in assuming my bike does NOT have the Starter/Headlight switch like the 750s do (headlight turn off during starting?)  If so, then my problem is either:

Bad bulb
bad wiring
burnt fuse
bad "hi/low" switch

Is there a good troubleshooting flowchart for this problem?  I looked through the archives and didn't see much that applied to the non start/headlight switches.

Any help would be great.  Bike runs perfect with the exception of the non-functional headlight.  Thanks!

[punch455]

It's a pretty simple circuit to check - doesn't even use a relay like all high current draw systems today. Do you have a test light? Do you know how to use it?

[sepling]

Yup, multimeter and test light.  I just wanted to make sure I can eliminate the start switch-- that seemed to be the problem on bigger bikes as I looked through the archives.

If so the entire circuit is battery to fuse, to hi/low switch to headlight.  Easy.  I'll start at the headlight and work my way back.

[Bodi]

yes, the starter switch does shut off the headlight on a 400F.

[sepling]

Troubleshooting

Go directly from the pos terminal of the battery into the dimmer switch (at the mass of connections under the tank), headlight works in high and low beam.  The dimmer switch isn't getting power through the black/white wire.

Black white wire goes back to the fuse box, goes through the headlight fuse, then turns black/red as it heads up to the starter switch.

So the starter switch should normally make the connection to the headlight when running but MAKE the starter connection and BREAK the headlight connection when you push the start button.  So if I'm right, there is a bad connection in the starter switch when the button is normal? 

Does this sound right?  Is this a common problem and what's the best way to clean/fix this switch?

[CBGBs]

Does the starter button work? There is a plastic form in the contacts of the button that always crumbles with age. It very typical. Check the button too.