Topic: Oh yeah, that electrical issue.

[CBGBs]

Hello all. I haven't posted much lately because I've been low on spare time and because I've been so bummed about not having a working bike, but I'm riding again. Now I recall that electrical issue from last year.
The main fuse is getting very hot and infrequently blowing. I've just installed a fast acting 20A fuse inplace of the 15A. This is just temporary.
The bike must have a short somewhere, but where?
The bike is also going dead electrically and when I turn the key off and back on it will come back as if the ignition switch is going bad.
Do you think these are related and will I have to replace the ignitioin switch and get a new key or can I salvage this one?
How do I check these?

[jdigga]

You can just unplug your ignition and bypass it with some wires to see if your bike will run w/o the switch.  My bike has a bad ignition which blew the main fuse.  I have a toggle switch in the meantime.  The left front turn signal wires were also pinched against the steering stop and shorting there.

[CBGBs]

So you think these are related.
I'd hate to have to carry two keys if I replaced the switch, but I guess it's better than my problem. I don't really want to rig a toggle on the bike.
Have you tried to repair the switch?

[jdigga]

No, I haven't repaired it yet.  The PO put the toggle in, so he cut off the connector in the headlight bucket too.  I don't like having the toggle (at least I can still use the fork lock), but on the other hand it's convenient to be able to have the bike running and still be able to open the gas tank and seat.

Partsnmore has a repair kit for the ignition which just replaces the base.  It's in the 750 section but not in the 400.  But your ignition should be the same as the later 750's so it ought to work.  Get to keep your same key too.

[bryanj]

if fuse gets hot its usually corroded or not tight enough connectors, and that base fits the 400/550/750/gl1000/cbx1000

[CBGBs]

I've cleaned the terminal on the fuse and its tight enough that it takes some effort to pull the fuse. It seems held in with moderate force but I'll check it again. Thanks

[Bodi]

Remove the fusebox (disconnect its plug or the battery first!) and check the wire connections inside.

[jdigga]

Yeah--the back of my fusebox was pretty crusty.  Also, I remember on the connector for the right control in the headlight bucket, I found one pin that had some corrosion on it.  So you might want to check the connector on your ignition as well for crud.

[CBGBs]

I'm trying to clean and inspect the switch. I've found the plastic clip on its bottom to be very difficult to remove. I havent gotten it off and the plastic is brittle so I can't pry with much force. I have push the steering lock pin out in hopes that the cylinder would just slide out the bottom with the platic tabs both pressed, which is very difficult with only two hands, but it's not budging. I may have to just get a new switch from ebay for about $30.

[jdigga]

I busted mine too trying to take it apart.  But it was a bad switch anyway so it doesn't matter.  I may harvest the one from my 79 but like you I'm not thrilled with having to have more than one key.

[TwoTired]

The fuse normally draws about 2/3 of its rating unless you've made changes to the bike; headlight wattage for example.
This will make the fuse warm but not hot.  You should be able to hold your thumb on it.

If it is hotter than this than you may have a restriction nearby for current flow.  Clip corrosion, clip misalignment, wrong length fuses, and poor wire connections on the back of the fuse block can all cause excessive fuse heating.

You should also check your battery voltage while reving the engine with a fully charged battery.  If your regulator is not limiting battery voltage to 14.5 V, the extra voltage causes extra power draw in the electrical system, which may overcurrent your main fuse.

Cheers,

[KCs76Cafe]

The fuse normally draws about 2/3 of its rating unless you've made changes to the bike; headlight wattage for example.
This will make the fuse warm but not hot.  You should be able to hold your thumb on it.

If it is hotter than this than you may have a restriction nearby for current flow.  Clip corrosion, clip misalignment, wrong length fuses, and poor wire connections on the back of the fuse block can all cause excessive fuse heating.
Cheers,

I too am having this problem. I popped the main fuse awhile back, up inside the endcap where I couldnt see it. Had me stumped for awhile since I couldnt see it was blown. If a cop had of rode by, he probally would have thought I was stripping the bike of its parts. Had the sidecovers and tank off trying to find out why I didnt have any juice.  Finally saw the fuse had popped inside the cap and I was on my way again.

Friday morning was on my way to work and I lost power again. Figured the fuse had blown so I cut the ziptye securing the bottom sidecover tab...<<<<insert blame on the PO   ...checked the fuse and it was good. Wiggled the contacts and I had power again. So I make it to work after fighting to keep the now "nonsecure" sidecover on.  Get home Friday after work,cut the ign switch off, then for the heck of it, back on and no power.  I wiggle the contacts again and they are burning hot. 

Tomorrow will go thru the connections behind the fuseblock, probally to find a cruddy mess. Will clean it up just to get me thru until my 4 fuse ATC style fuse block gets here. Planning on doing the relay upgrade on the headlite as well. Might as well get rid of all the gremlin prone areas at once and be done with it.

Sorry for the rant....just figured I would add my electrical woes into the pot.

[CBGBs]

The fuse normally draws about 2/3 of its rating unless you've made changes to the bike; headlight wattage for example.
This will make the fuse warm but not hot.  You should be able to hold your thumb on it.

If it is hotter than this than you may have a restriction nearby for current flow.  Clip corrosion, clip misalignment, wrong length fuses, and poor wire connections on the back of the fuse block can all cause excessive fuse heating.

You should also check your battery voltage while reving the engine with a fully charged battery.  If your regulator is not limiting battery voltage to 14.5 V, the extra voltage causes extra power draw in the electrical system, which may overcurrent your main fuse.

Cheers,

Thank you two tired for all of the extremely useful advice. Excellent post.
I put the switch back together and clean and greased the connections on the switch and the fuesblock connector. I went for a test ride and things seemed fine. It has been a bit intermittent though, so I'll have to keep my eye on it. I'm going on a group ride today so I hope it holds up. I plan on getting a new switch from Partsnmore. They are only $22 and shipping is only $3.

[750duo]

I would not wait too long to find an electrical overload problem. 

If you keep INCREASING the value of the FUSE, the fuse will be capable of carrying more current than the WIRES. 

The purpose of the fuse is to limit the amount of current to an amount lower than the current carrying capacity of the wire. That is - The fuse will blow before the current is high enough to BURN - I REPEAT - BURN - the wire.(With REAL FLAMES AND CHARRED WIRING - Ruins the heck out of your paint job and requires replacing the electrical system components, paint, seats, etc. - I know from practical experience)

If the value of the fuse is high enough - the wires become the fuse.

Dangerous Situation

[CBGBs]

This does sound dangerous. I'll get some 15 ampers in there, but today all is well. The bike had no problem with bad contacts or warm fuses. The bike needs the carbs sync'd but is still pullin hard all the way up. Wooo Hooo! I had a blast!

[CBGBs]

I have just replaced the ignition switch and will now test the voltage of the bike while running.
I was thinking of an alteration to the stock bike that may be an issue.
I replaced the right control switch with one from another model bike. Mine had the usual deteriorated plastic clip. Since the wires were a bit different I had to figure things out. Now the kill switch will start the bike in the OFF pos. The bike does not start in the RUN pos.

I don't get it but the bike ran so I figured I had an anti theft device, since only I knew how to start the bike.
Perhaps this is causing the problem. Any ideas?

[CBGBs]

I've taken TwoTired's advice and tested the voltage of the battery off and with the bike running at 3000rpm.
Off the battery was showing about 12.4v and with the bike running it was showing about 15.1v. This would seem to indicate that the rectifier is not limiting the voltage to 14.5v. The headlight was not on because my lowbeam is out.
Is there another test to determine whether I need to spend the $50 on a rectifier?

[TwoTired]

The rectifier converts the AC (alternating current) from the alternator to DC (direct Current) that the battery can use.

Your test seems to indicate the rectifier is okay.  However, your regulator is suspect.  The regulator is supposed to reduce the voltage across the White and Green wires going to the alternator field coil when the voltage at the battery gets above 14.5 V.  When the battery voltage gets above this level the white and green voltage should be less than what is on the Black wire going to the regulator (Much less when the battery reaches 15V).  When the voltage goes below 14-ish volts, then the white and green wires should have the same voltage as what feeds the regulator on the black wire.

If your regulator doesn't behave as described above.  You may well have to replace it or repair it.

[CBGBs]

I thought the regulator and rectifier were one unit. Is the regulator the unit on the left of the fuse box in the first picture in this thread. The unit with the black green and white label?

[TwoTired]

From the factory, the CB400F came with a separate regulator and rectifier.  There are units made that combine the functions.  I don't actually see the rectifier in your photo.  But, the regulator has those black white and green wire connections.

Cheers,

[CBGBs]

Thanks dude!

[mmtsquid]

I JUST HAD this problem with the fuse box!
What I discovered is the the clips holding the main fuse had corroded in the back, by where the wire is soldered to it.
I'm trying to find replacement clips now.........

[Bodi]

Measure the voltage between battery "+" and the black wire on your regulator. Whatever voltage you get is due to assorted resistance in the wiring harness and switches. This voltage confuses the regulator, it uses the black wire as its reference voltage. SO, if the regulator is working perfectly and controlling the black wire voltage at 14.5 volts, the battery will be at 14.5 volts PLUS whatever voltage you measured between the battery "+" and the regulator black wire. This is a frequent cause of a battery overcharging and "boiling" dry.
So check this before replacing or readjusting the regulator. Cleaning all the harness connections and switch contacts will help keep the voltage drop to minimum.
Adding an automotive relay to connect battery "+" directly to the regulator terminal (through a fuse for safety) when the ignition is on helps the regulator control the battery voltage better.