Topic: 1978 CB400 Electrical Issues? I think...

[MikeJames]

Hey Y'all, I am brand new to this site with very little knowledge of bikes, but I am attempting to learn. I bought a 1978 cb400 about a month ago with 5k miles on it. Running great, until one day it shuts off while in 3rd gear then 4 hours later turns on goes about 5 miles to my house.

Now most of the time it wont start, except for random occurrences, but then will die a couple minutes later. I had a mechanic clean & replace a carb since it sounded like it was starving for fuel. He told me he thinks its the CDI, I thought if it was the CDI it wouldn't start at all?

Any suggestions on what it could be or what I should test is welcomed & much appreciated.


I apologize for my lack of knowledge...

[Tim2005]

Is it a 4 cylinder cb400 or a 2 cylinder one?

[calj737]

If its a '77 400/4, then it doesn't have stock CDI, it has points/condensers. If its a '78, then is it the Hawk/Hondamatic? That year and model have CDI. Can you post a picture of the steering neck VIN plate to confirm the model?

[Airborne 82nd]

If its a '77 400/4, then it doesn't have stock CDI, it has points/condensers. If its a '78, then is it the Hawk/Hondamatic? That year and model have CDI. Can you post a picture of the steering neck VIN plate to confirm the model?

Or the number on the engine.

[MikeJames]

Sorry about the confusion but it is a 1978 Honda CB400TI Hawk I

[Rob69]

When the bike fails to start, have you checked for ignition?

[calj737]

Well you're not giving us much to go on...

You need to perform some diagnostic steps:
1. Battery voltage - Measure it with a meter with no key ON
2. Verify fuel flow to carbs
3. Verify power to the ignition (you'd be surprised how many times a loose power wire to the CDI can be intermittent problems)
4. Verify spark from to the plugs

Then report back on these findings and we can help you dial it in.

[MikeJames]

I have charged the battery, checked the voltage, verified fuel flow to carbs..

Im getting new spark plugs today to replace.. Not sure how to check the power to the ignition, but I will do that. Its a kickstart only

[calj737]

From your KILL switch, there's a BLK/WHT wire running to the coils. Use a meter and verify you have 12v at the coils with switch set to RUN

[MikeJames]

Checked the following & all of these things are working..
1. Battery voltage
2. flow to carbs
3. power to the ignition
4. spark plugs

Any other suggestions?

[calj737]

Checked the following & all of these things are working..
1. Battery voltage  What was it?
2. flow to carbs How about float level via clear tube method?
3. power to the ignition to the coils or to the plate? What voltage did you get?
4. spark plugs that you have them, or that they aren't fouled? Can you post a picture of them?

[MikeJames]

1. Battery voltage was 12
2. I am not sure how to do that but I will look into that
3.  power to the coils 12v.
4. Brand new spark plugs

[Rob69]

1. Battery voltage was 12
2. I am not sure how to do that but I will look into that
3.  power to the coils 12v.
4. Brand new spark plugs

Is there spark at the plugs?

Sent from my C6730 using Tapatalk

[calj737]

Is there spark at the plugs?

Its a bit like pulling teeth...