CB400T Carb repair, etc

crazypj said:
I only ever recognise oak and pine, everything else is just 'wood' :LOL:
I do have a few bits of Florida Holly, had to remove a tree some friends planted when they moved, always promised to make a pen but never got to it.
Click to expand...
Holly is a nice wood to turn.
I find that making pens is an enjoyable little hobby.
well.........
until a lamination blows up in your face at 3000 RPM.
bob
 
My friend that purchased the 1981 CB400T from me is stopping by tomorrow, the headlight is no longer working.
I asked if the high beam worked, he said no.
Any guidance as to where I should look, other than checking the bulb first?
bob
 
We just had another similar thread so it is still fresh in my mind. Assume that the lamp is fine, headlight fuse next, then check for battery voltage both side of the headlight fuse, black/red and black/yellow. If no voltage go to starter button.
 
OK, I had a look at the headlight issue.
The light is good, I checked it with the meter and connected it to 12V, both beams work.
I checked the fuse(s), all are good.
I took the high/low switch out and checked it, it seems to work.
for some reason I do not have juice at the switch or at the light.
I am charging 12.5V when idling also.
so.........
because this is obviously over my head I made a short harness.
Connected it to the low beam and return on the light itself.
ran the harness with an SAE 2 prong plug on it, and back to the battery.
When he starts the bike, he connects to the battery charge pigtail, and has a light.
I need to give this more thought.
Electrical problems are not my favorite thing to tackle.
bob
 
Possibility the indicator ground lead is connected to a black power wire?
The ground on those, instead of being a green wire, was a black with about 1/8" long green tube that is easy to miss or may just have fallen off over the years.
If you have power on black wire to handlebar switch it has to be coming back out on either white or blue (probe connectors with a paperclip, one leg straightened out then flattened with hammer(or two if you don't have a vice or bench block)
 
Power for the headlight runs through the electric starter button, you say the fuses are good, but did you check for voltage at the middle fuse?

If you have the materials to make a fused pigtail, then inject voltage at the middle fuse and see if the light works.

If you are not getting power on the black/yellow wire, then start looking at the right handlebar switch
 
crazypj said:
Possibility the indicator ground lead is connected to a black power wire?
The ground on those, instead of being a green wire, was a black with about 1/8" long green tube that is easy to miss or may just have fallen off over the years.
If you have power on black wire to handlebar switch it has to be coming back out on either white or blue (probe connectors with a paperclip, one leg straightened out then flattened with hammer(or two if you don't have a vice or bench block)
Click to expand...
Thanks, I'll try this out.
My gut tells me that the handlebar switch is causing issues.
When I owned the bike I had some trouble going between high and low bean.
Because I never rode at night I just left it in low and never touched it.
bob
 
esmith250624 said:
Power for the headlight runs through the electric starter button, you say the fuses are good, but did you check for voltage at the middle fuse?

If you have the materials to make a fused pigtail, then inject voltage at the middle fuse and see if the light works.

If you are not getting power on the black/yellow wire, then start looking at the right handlebar switch
Click to expand...
Thanks for the advice guys, again!
this site is just the best!
bob
 
On my CM400 all the headlight amps go thru that right handlebar starter switch, it disconnects headlamp when pressing in starter button to allow more amps for starter. Subject to spark/oxidation with all those amps going thru it. I have to wiggle my starter button and place hand in front until I see it go on. Have tried cleaning it a few times with mixed results, that can be challenging to take apart the starter button enough to do a good job. Switched to LED headlamp on the 82 CM450 and that I really enjoy simply not having to fret over all those amps going to traditional filament headlamp, the LED take about 1/10th the amps. On my 2005 Ford Escape I had an oxidized connector right at the headlamp and it melted the plastic housing, an example of what can go wrong with all those amps.
 
a question.....
Is there a good copy of a CB400(T) wiring diagram out there?
when I zoom in on the one in the service manual it gets fuzzy fast.
just thought I'd ask.
bob
 
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