1982 CB750F...Better Devil

irk miller

You've been mostly-dead all day.
DTT BOTM WINNER
Do you have the stock handlebar control? I can't remember without digging back in the thread. I'm running a stock replica Honda control on my CB550/650 hybrid and it has a switch that turns running lights on and off.
 

Jimbonaut

Well-Known Member
DTT SUPPORTER
Yeah it's stock (if you mean the headlight switch, and run/off switch). I did have to meddle with them as I had all kinds of problems getting the headlight to come on, that's now resolved.
 

Maritime

Well-Known Member
That's where it could be, under the switch where the wires are soldered in sometimes one of the wires can snap off. Or sometimes the splice for the 2 browns gets broken. so look right at the bottom between the switch and the connector for a bad wire.
 

Jimbonaut

Well-Known Member
DTT SUPPORTER
Ah, but it's a brand new harness. The connector on the key barrel itself is the problem? Do I need to take that thing apart?
 

Maritime

Well-Known Member
Not the connector no because the light works in park, the issue is someplace in the ign switch wires themselves, you can take it apart and it may be corroded, broken etc. I had the tailight wire snap off inside the housing on my CM, I re-soldered it and it was fine again.
 

Jimbonaut

Well-Known Member
DTT SUPPORTER
So I gotta take the column apart? I remember having a look at the thing a while ago but don't remember seeing any way of disassembling it.

Recently discovered Nine Inch Nails' Ghosts V. It's chilled as a hindu cow so I'll sling that on while I disappear down another wiring rabbit hole...
 

Maritime

Well-Known Member
OK so I looked at your switch does it look like this one?

https://www.ebay.com/itm/Ignition-S...312525?hash=item4b7558f98d:g:3xgAAOSwxrJemw1w

if so there are no wires to break but there are contact pads inside that can corrode and not pass power. you can open some of them and give it a good clean up and some you can get just a replacement bottom so you can get it working and keep you key. You can use a test light or multi meter to see if there is power coming out of the terminal for the tail light pin when in "Run" vs "Park"
 

Maritime

Well-Known Member
Pop the little tabs and look at the copper inside there and it may be all green and cruddy and not sending the power out well on the tail connection. you can power on the bike with the harness plugged in and test the wires right at the plug in run. the red is 12V in and then there should be 12V out of 3 of the pins then when in park is should 12V out of just 1.
 

Jimbonaut

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DTT SUPPORTER
Yup, that's the bugger. Any idea how to open it up? Also, re. the multimeter/test light. My nemesis(es?). If the column is connected to the harness how would I get a probe on any of the terminals? Sorry for the dumb question!

Edit - we posted at the same time. Cool, that's how to open it up. I don't understand though how to test power through the thing - should the column be connected to the harness when I test?
 

Maritime

Well-Known Member
I tried giving you a call to splain it better but before you take it apart you can test the wires at the connector with a light. Ground the light someplace on the frame, then turn the key to run and check the wires coming out of the plug. Red should light, blue should, brown white should and brown should. If brown doesn't, put in park and try, if it does then the switch is buggered and you want to open it up. If brown lights at the plug in run, there is a problem in the wire further down.
 

Jimbonaut

Well-Known Member
DTT SUPPORTER
@Maritime, you’re a legend mate. Dismantled the ignition column, got to the white switch part on the bottom and managed to pry inside it enough to clean up the contacts. Sure enough one was totally corroded and really green but wriggled a needle file in there and cleaned it up. Taillight working just fine now ...




Sent from my iPhone using DO THE TON
 

Jimbonaut

Well-Known Member
DTT SUPPORTER
In case anyone reading this finds themselves in the same boat. Here's what the ignition switch looks like from the top (once you've managed to pry the bastard off the main metal column - there are three tabs that need to be pushed in to release the switch) -



The white, top part apparently is removable (I couldn't get it to come off but it can be) but if you rotate it just right you can just see the contacts underneath -



Then you can pry a needle file in there just enough to clean off the corrosion from the contacts (mine were proper green) and you're in business -



At least, that's how I did it.
 
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