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1997 CB400 Four charging issue 🤯

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Gaz_hay:
Good evening,

I have recently purchased a Honda CB400 Four
1977
I’m planning on restoring bits myself , but I have no idea where to start on the charging issue, I have use of a multi meter and some basic knowledge on using it…
But I have zero knowledge on the cb charging set up , and never had any knowledge or experience with the stator especially with a “field coil”

Hopefully some gurus on this group can help me out , any information or ideas where to check would be much much appreciated 👍👍👍

McCabe-Thiele (Ted):
I assume when you mention charging issue that it's not charging.
I would start with checking the first connector block from the alternator, it might just be corroded terminals in the block.
Next I would check the connections to the voltage rectifier and the voltage regulator.
Also check the main earth connections, loom to frame, engine to earth strap etc.

If the above do not work then its worth using the search facility on here for checking the alternator field windings etc its a pretty regular area of discussion so you should come up with plenty of threads/posts on the subject. I have never had to go beyond the basics  with my 400 so I can't advise on the more complex aspects.

Bryanj:
There is a 6 page bulletin explaining the 3 phase charging, i have tried to screenshot and post

Bryanj:
3 wiring diagrams to go with details

exvalvesetdabbler:
If the field coil is energised it should attract a metal spanner if you hold it  close to the honda logo on the alternator cover with just the main switch on

If that doesn't happen it narrows down which connections it might be.

Charging at low revs the field coil is fed the full 12v from the regulator. As the revs go higher a contact opens and the field coil is fed from a wire wound resistor under the metal back cover on the regulator.  So if your getting little or no charge at lo revs that suddenly bursts into life as the revs increase, there may be a grubby contact in the regulator. At 15v another contact shorts out the feed to the field coil.

The shop manual downloadable from Ash's Dropbox might help regarding what revs the regulator should switch over.

As mentioned in a previous post , spraying the connectors with wd40 or duck oil followed by plugging unplugging a few times to wipe the contacts might work if the connectors are grubby.  There is also the 3 spade connectors that go to the regulator.

Regards
Dave

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