Topic: 75' CB400F Electrical Problem (New Member, New Project)

[redvette23]

Hey guys I am new to the forms here and also new to bike repair and rebuilds.  Just got a 75' CB400F with 9,xxx miles and looking for a little (but much needed) help.  I've done some old jeeps in the past and this is my first bike that I'm hoping to restore; maybe even do some cafe mods.  First things first: she's got some electrical problems.  Turning the ignition gets me no lights, signals, or cluster notifications whatsoever.  Kick starting also shows no spark at the spark plugs.  So far I have found a green wire with a red stripe coming off the starter solenoid that does not have electricity flowing through it.  If I am correct, it goes to what looks like a fuse? and from there to the alternator as a lighter green with a red stripe wire.  Please bear with me if some thing doesn't make sense: I haven't had to do too much electrical work in past projects.  Corrections are welcome and so are questions if I am not specific enough.  I'm thinking about trying to bypass the starter solenoid with a screwdriver across the terminals.  Is this a good idea or are there some other things I could look for?

[RickB]

Redvette,

You've got some learning ahead of you for sure, but when I started I knew nothing, I mean nothing, about motorcycles or mechanics really.

Have a look through my CB400F rebuild thread, chances are I've had the same problem you're having, or will have, at some point.

You'd do well to purchase both the Haynes and Clymer manuals. Besides these forums, they're very handy. I would get a hold of the wiring diagram (search the forums, or in the rear of the above mentioned manuals) and trace things back.

As for this specific problem, it doesn't sound like you have power at all. From your limited description and photos, it seems like your wiring is correct. Pull the fuse cover off and make sure they're all good. Specifically your 15A main fuse. Have you got battery power? Have you got a multimeter? It'll be hard to diagnose any real electrical faults without one.

Welcome aboard.

Rick.

[twinegar]

......I agree, get the wiring diagram and check the battery and main 15A fuse and also the ground cable at both ends before doing anything else.  You will also want to go into the headlight case and unplug-replug every connection to cut new metal. Working back do the same with any other connections you see including the coil inputs. There will be a small green ground pigtail coming off the main harness and bolted to the frame, make sure it has a clean connection. The 15A wire in the fuse block can get real hot if there is an accumulation of oxidized connections in the system. If the main fuse is blown, that is probably the reason. As far as the 75 CB400F goes you have a real classic there that continues to grow in market value..............as long as it is kept in original condition. Post some pictures, I am curious to see just how original it is and especially the beautiful original exhaust system. The right sweeping header pipes is considered one of the best looking arrangements ever placed on a bike.


Magazine article: http://www.spookytoms.com/Magazine-MS675CB400FA.html
Sales Brochure: http://www.spookytoms.com/Brochures-1975CB400F.html

[redvette23]

Thanks guys, I have battery power and fuses are good.  Also been doing the testing with a multimeter hopefully I can get some photos of my reads tomorrow.  Rick just want to say your build got me inspired to pursue this I'll be going through it again.  I've been working my way through some shop manuals and the wiring diagram also.  Twinegar thank you it's as stock as they come right now, I'll post an update tomorrow on what I find with the ground cables.

[DarcyCB400F]

welcome to the forum!
I have a very complete and detailed wiring diagram for a 400F.
Accept no substitutes!
PM me with your email address and I will send you a high def version of it.

[SanDogDewey]

A bad RH stop switch can prevent the bike from getting power. Methodically trace power from the battery to the starter and to your coils. You'll find it.