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Discussion Starter · #1 ·
Greetings all.
I'm moving on to the next challenge with my CB400T.
The green neutral light shows on the dashboard when I first go to the bike.
And the bike can be started, either on the kickstart or the electric start.
But when it has been running for a few minutes or if I come back to it a bit later the light is no longer illuminated (actually it seems to be really dim but I suspect that is just spill over light from the red charging light)
In this state I can still kick start it but the electric start will not work.
I've looked at the wiring diagram and seen an old post here that points to the neutral switch and how well it is earthed.
My 101 question is - where is the neutral switch? (Clymer not giving me any clues).

Supplementary question - I see from the wiring diagram (in Clymer) that there is a clutch switch that seems to connect to the starter magnetic switch.
Does this mean that I should need to engage the clutch in order for the electric starter to work? (which is not the case at the moment).

Thanks in advance and all the best from Auckland.

David

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dash with neutral light on.jpg
 

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First use the clymer manual for a door stop and pick up a FSM. I have not worked on a CB 400. If its like the other 400s the motor runs off the stator and it will start and run
without the battery. The electric start will work with the clutch lever in or out if the motor is in neutral . If in gear you have to pull the clutch lever in to start it in gear . The neutral switch is located on top of the upper case under the right carb. I suspect you have a bad ground or connection. Hope this helps.

Note, the battery is for the starter and lights. The stator and CDI are AC .The three yellow wires from the stator go to the REG/REC and are converted to DC for the battery and lights.

Bill H
 

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Discussion Starter · #3 ·
Thanks very much Bill.
So I located the neutral switch (thank you) and cleaned the connection.
Whilst I was there I did the same for the main ground connection (which was already pretty clean).
Then I tried the start routine again.
First time; neutral light on and it started just fine on the electric starter.
Ran it for a few minutes, turned it off then tried again.
Neutral light still on but this time not a peep from the electric starter, but fine with the kick starter (which when I think about it, may have been what was happening yesterday, sorry...)
I checked the bullet connector that the neutral switch wire goes to and that looks untouched, original and fine.
The main connection into the starter motor is also good; I cleaned it up the other day when I had the starter motor out.
So my attention turned back to the wiring diagram and I thought I would check the connections on the starter magnetic switch.
They looked fine but thought I would take them off, clean them up and then refit.
And that's as far as I got because when I went to disconnect the top wire the whole bolt started to spin and I don't have a slimline spanner that will hold the bottom nut whilst I undo the top one.
So tomorrow's shopping - or grinder - chore.
Or any other suggestions welcome (I can't think of any other ground connections to check....).
Photos attached because I can :)
Thanks again.
David

20210530_152259_resized.jpg 20210530_152804_resized.jpg 20210530_154711_resized.jpg 20210530_161436_resized.jpg
 

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Hi David. The neutral light and power to the starter are on the same circuit so if the neutral light is out there is no power to the starter. If the whole bolt is turning on the magnetic switch I would think the switch is bad cause its not suppose to do that. . I think I would replace the magnetic switch and see if that didnt take care of the problem. I have a wiring dia so if the magnetic switch doesnt repair it I will dig into the dia and se if I can help you out.
 

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Discussion Starter · #5 ·
Thanks Bill. I will try a new magnetic switch as you suggest. Might even push out of my comfort zone and try a bit of diagnostics on the old one :). Your advice is greatly appreciated....
 

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Discussion Starter · #6 ·
Thanks Bill. I will try a new magnetic switch as you suggest. Might even push out of my comfort zone and try a bit of diagnostics on the old one :). Your advice is greatly appreciated....
Okay - I have had a few days away from it, firstly waiting for the new starter relay to arrive and then waiting for a bit of stability before hitting the starter button as I had the bike on blocks to do the front fork seals.
To recap. Previously the bike would start from cold on the electric starter but then not the second time onwards / when it was warm.
I fitted the new starter relay with great optimism that it might solves all of my woes but not to be; it seems the 400T still has a few things she wants to teach me :).
This time - with the new relay - no response from the electric start, when cold or otherwise.
So I thought I would put the old starter relay back on. Still nothing i.e. nothing happens when I hit the starter button.
I also took the neutral switch out of the crankcase and - following advice to someone else's post here - got excited when I read about the aluminium washer needing to provide a good earth. Cleaned up said washer plus the switch itself and the crankcase it contacts. No difference.
Next I put the new starter relay back on and in the process cleaned up all of the terminals and contact points. Still nothing.
Had a quick look at the "other end" of the orange and green wire i.e. where it connects to the rectifier / regulator under the left side cover. This looked okay but I gave it a squirt anyway. Still nothing.
The bike is generally pretty tidy and the wiring all looks quite original to me i.e. unbutchered, as per photos:
20210606_132647_resized.jpg 20210606_132700_resized.jpg
The neutral light appears to be properly showing i.e. on when I go to start it, but when I rode the bike yesterday I noticed it was only working intermittently.
Any further thoughts or suggestions are most welcome...
 

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I am looking at the 78 CB 400 t wiring dia. I dont see an orange green wire to the rec/reg. I also dont see the starter button . Go back to the mag switch an tell me what color the wires are from the switch to the bike . I am seeing a Y/R and a G/R . G/R to clutch switch and Y/R to ing switch . Is this correct. Or does the Y/R go to the starter switch.
Thanks

Bill H
 

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Discussion Starter · #8 ·
For the wiring diagram I'm looking at "1978 & Later CB250T Dream 1978-1979 CB400T2 Hawk Type II" in Clymer (I know....).
Mag switch has a Y/R and G/R connecting to wires of the same colours in the loom, which matches the diagram.
G/R to clutch switch, Y/R to starter button.
Photo below:

Y&R and G&R from starter solenoid to bike.jpg
I'm thinking I should check the starter button next (although it seemed to be okay a while ago...)
 

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I was going to suggest taking the starter switch off and inspecting the inside today but you beat me to it.

Bill H
 

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Discussion Starter · #10 ·
I was going to suggest taking the starter switch off and inspecting the inside today but you beat me to it.

Bill H
Thanks Bill. Just to let you know that this is a work in progress; took me two days to get the handlebar assembly apart and now it's a similar challenge with the switch screws. I'm trying to be patient and applying copious amounts of penetrating oil but I guess that after 30 years it's no surprise that things are a little stuck in their ways.... Will report back.
 

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I have had several of those apart and yes the are a chore. You might jump across the switch and see if the starter works and see if the switch is the problem.

Bill H
 

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Discussion Starter · #12 ·
Jumped
I have had several of those apart and yes the are a chore. You might jump across the switch and see if the starter works and see if the switch is the problem.

Bill H
Had some quality Honda time with a friend this afternoon. Checked the wire from the switch to the relay which seemed fine. We were about to try to understand how to jump across the switch - which was still screwed firmly in place and not showing any signs of budging - when we noticed that the contact to ground was pretty rusty. Cleaned that up, reassembled and the switch seems to be working just fine now. So thanks for the tip Bill and regards from Auckland....
 

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Discussion Starter · #13 ·
Well not quite there yet. Put the tank and seat back on all excited to take it for a ride and.....no response when I press the starter button. Loosen the two screws and try different positions of the clamp onto the handlebars assuming it was a ground problem there. Still nothing. Kick it and go for a ride; great day here. Back to the switch tomorrow I guess...
 
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