total electric loss

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total electric loss

Honda Cb400 super four, no mods, version S.

Riding late last night, suddenly all electrics went out and engine stopped as if i'd turned the ignition key to off. Checked the 10A fuse's and all intact. Though i found the + battery connection was very loose, almost off so i tightened it up but still no power. I thought there might be a 20A ignition fuse that had blown but cannot locate one (not too good with electrics).

The bike is now as if there is no battery connected, cannot even push it off. Any help appreciated.

Now found the 20A fuse, intact. Just a clarifacation, i was doing 100kph when the electrics went out. The lights all went out inc dash lights though the engine, in gear and doing 100kph, turning over should have kept the lights on until it stopped. It didn't.

Good info. Bikes generally have a fusebox full of 10A, 15A and sometimes 20A fuses controlling the lights, ignition, signals (including horn) etc. They usually also have a 30A "main fuse" piggy backed onto the starter relay. This will be near the battery, on the big fat cable that runs from the battery to the starter motor. Check this fuse and the state of sockets it plugs into - eventually they rot and depending on the way your bike is wired you can lose all electrical power. Other than that if the fuse and its connections are OK and you're getting power on the feed up to the ignition switch, then it must be an ignition switch problem (the switch is below the ignition lock, it's not the lock itself). If the fuse hasn't blown then it can't really be a short circuit...

Incidentally, "version S" doesn't really mean much. They were all "CB400SFxx", but some of them were just "SF", some were "SFV (Vtec) etc. I do have a couple of wiring diagrams. What year is your bike and does it have VTEC?

Thanks for that, mines pre-VTEC

hi i have a cb400 sf as well, but i have no power at all when the key is turned on, no lights etc, mine happend the same way as carl any idea on what is wrong with it, its a new battery, just fitted a new starter relay today thinking it was that. i have no idea about electrics many thanksĀ 

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