Topic: Just one more thing before I can ride it - CB750 K6 tail light ???

[greenjeans]

76 CB750K   100% stock

Bike runs like a top.  I can't seem to get anything at the tail light.   Headlight is always on - no off switch on the controls.  Both brake light switches work - I'm getting a brake light from both the rear and front.
Harness is new, all wiring in headlight bucket has been checked and rechecked.
If you turn the key all the way, the tail light does come on.

Getting continuity with the wires into the harness (green, green/yellow and brown)

tail light receptacle is known good - came off a running bike.

Where should the tail light be getting power ?
I'm off to check the fuse which if it was burned out, I wouldn't be getting anything right ?  Fuse is good

Then check for continuity from the ignition to the tail light (brown) ??

Any ideas ?  Every other light, bell and whistle works.  Idiot lights all work as does the annoying turnsignal buzzer

[greenjeans]

changed the ignition switch to a known good switch (identical).   Still not getting power to the tail light.

All other functions of it work - both brake light switches front and rear, and the parking feature.

However, the switch from the known good bike is a 74.   The switch, and wiring colors are identical -

Does the 76 have a different switch ?   

[ekpent]

Sounds like the 'bright' filament is getting power via the brakes. Have you tried a different bulb yet ?   What you are saying I think is that you do not have the continuous running light when the headlight is on but the brake filament is lighting/working ?

[seanbarney41]

check the fuse, I recently had the same problem with my f3, I think somehow the brakelight and emergency light are not fused.

[greenjeans]

correct - bulb is good.   brakes are on one filament, the parking and running are on the other.  Parking feature works, so I know the bulb is good.  Even tried 2 more - even though I knew they would not work.

Every single thing else on the bike works like a champ.   I'm just not getting the running light - which is no biggie in the day time.   I just can't ride this thing at night.    Can't for the life of me figure it out.

Even grabbed a different fuse box from a "known good" bike.   Still nothing.  New fuses as well - all checked for continuity.

[mrbreeze]

Bad ground?

[greenjeans]

Ground is solid.

Here's the wiring diagram that I'm using.   I just noticed that there is a brown/white wire that jumps from a 4-way connector in the headlight bucket to another 4-way connector in the bucket with the black wires.  I'm pretty sure that I must have missed that one - I did have 1 wire left over that had no place to go.  Somehow, I'm thinking that it was brown with a dark horizontal stripe - not a white stripe running the entire length of the wire casing.

That has to be it right ?   Last night I traced the brown wire all the way from the tail light, through the fuse block and on to the ignition switch.  It's good, but has no power to it.

But... If I'm reading the schematic correctly, when the switch is in the "On 1 / run" position, black and red make a connection as well as brown/white and brown make a connection.  I still don't see where the tail light gets its power.

When the engine stop switch is in the on position the black wire should bring 12v to the connector in the bucket that has the rougue brown/white wire to it correct ?    That should do it ?

[DH]

I wrote about this earlier, but second guessed myself and earased my post.
 I THINK the tail lite fuse is fed power from the brown/white wire WHEN IN RUN position (position 1). That wire looks to be connected to a black switched power wire
located in the headlite shell. And The tail fuse is powered by the red, always hot wire
when the switch is in park (position 2) Try jumping red to black and brown to brown/wht at ign switch
That will give you (electrically) position 1, which should power up the tail fuse circuit
and light everything up. And if that does occur, the switch is probly bad.
You probably have it figured out by now tho

[greenjeans]

The jumper wire was it.   Can't believe I missed it, but luckily, the jump wire was still connected to the old harness.  All is right in the universe again.

Had I just looked a little harder on the schematic, I would have saved myself a couple hours trying other things.