Author Topic: Cb400/4 No power to points  (Read 4997 times)

Offline Coppertop1234

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Cb400/4 No power to points
« on: January 17, 2026, 05:36:55 PM »
Hi all been away for a while from the forum
wow last post was 2018 time flies
but the biking bug never dies.
Just playing with a 400/4 and no power to points

Powers up and turns over fine

Checked wiring connectors all seem ok
Replaced points condenser - same issue
kill switch seems ok
possible zenner diode fault?

advice appreciated
« Last Edit: January 17, 2026, 05:50:35 PM by Coppertop1234 »
I Love Tinkering with Old Classics
1970 Mobylette 50cc  
1972 Honda Cb175
1974 Yamaha Rd250  
1962 Triumph 650 Bonneville
1972 Norton Commando
1978 Honda CB400/4
1976 CB750F1 
1976 Suzuki GT750 Kettle
1978 Honda CB 750 F1 
Married Life No Bikes for a while then
1975 CB Honda 400/4 Restoration
1976 Kawasaki Z650   Restoration
2002 Suzuki GSX1400
1976 Honda cb750F1  Restoration
1978 Honda cb750 F1 Restoration
1977 CB 250 Dream    Restoration
1977 CB400/4  - The last one - Restoration

Offline Oddjob

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Re: Cb400/4 No power to points
« Reply #1 on: January 17, 2026, 05:50:38 PM »
Power to coils on the black/white wire?
Kids in a the back seat cause accidents.
Accidents in the back seat cause kids.

Offline Coppertop1234

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Re: Cb400/4 No power to points
« Reply #2 on: January 17, 2026, 05:53:38 PM »
will check them out tomorrow cheers
I Love Tinkering with Old Classics
1970 Mobylette 50cc  
1972 Honda Cb175
1974 Yamaha Rd250  
1962 Triumph 650 Bonneville
1972 Norton Commando
1978 Honda CB400/4
1976 CB750F1 
1976 Suzuki GT750 Kettle
1978 Honda CB 750 F1 
Married Life No Bikes for a while then
1975 CB Honda 400/4 Restoration
1976 Kawasaki Z650   Restoration
2002 Suzuki GSX1400
1976 Honda cb750F1  Restoration
1978 Honda cb750 F1 Restoration
1977 CB 250 Dream    Restoration
1977 CB400/4  - The last one - Restoration

Offline Coppertop1234

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Re: Cb400/4 No power to points
« Reply #3 on: January 17, 2026, 06:15:04 PM »
No power to coils
New battery fitted
??
I Love Tinkering with Old Classics
1970 Mobylette 50cc  
1972 Honda Cb175
1974 Yamaha Rd250  
1962 Triumph 650 Bonneville
1972 Norton Commando
1978 Honda CB400/4
1976 CB750F1 
1976 Suzuki GT750 Kettle
1978 Honda CB 750 F1 
Married Life No Bikes for a while then
1975 CB Honda 400/4 Restoration
1976 Kawasaki Z650   Restoration
2002 Suzuki GSX1400
1976 Honda cb750F1  Restoration
1978 Honda cb750 F1 Restoration
1977 CB 250 Dream    Restoration
1977 CB400/4  - The last one - Restoration

Offline McCabe-Thiele (Ted)

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Re: Cb400/4 No power to points
« Reply #4 on: January 17, 2026, 07:06:54 PM »
I would start by checking the voltage from the ignition switch and work my way using the wiring diagram following the ignition feed  wire all the way to the coils.

Honda CB400NA Superdream (current money puddle)
Honda CB500 K1 (second money pit)
https://www.sohc.co.uk/index.php/topic,28541.0.html
Honda CB400 four super sport (first money pit)
Link to my full restoration http://www.sohc.co.uk/index.php/topic,23291.0.html
This is a neat 500 restoration in the USA.
http://forums.sohc4.net/index.php/topic,151576.msg1731556.html#msg1731556

Offline Oddjob

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Re: Cb400/4 No power to points
« Reply #5 on: January 17, 2026, 07:32:32 PM »
Coils are powered through the kill switch. Open the headlight and see if the switch has power and if so it's coming out of the black/white wire in the headlight. If not the switch is most likely dirty, simple to clean if it is. You could jump the kill switch by jumping a black wire into the black/white wire and see if it fires up, ignition switch on of course.
Kids in a the back seat cause accidents.
Accidents in the back seat cause kids.