Fuse Box fun and more...

[Athame57]

 I recently had a new harness (loom) fitted and new battery too. I soon needed a new rectifier and that was done. Then a black out on the street that turned out to be a couple of blown fuses, something the AA man overlooked    , my local bike shop sorted that out. A new condenser has been ordered as I saw a one on ebay. So I'm working on my electrics but not fast enough it seems. This morning all was dark when I turned the key. I noticed my headlamp switch was in the on position from when I last rode a couple of nights ago, I didn't see that doing any harm but took my battery in for a check in case, all was well with that.
I take off the side panel over the fuse box area and gave this tiny black square thing (arrowed in picture) a good press with the finger and all lit up fine. voom voom off I go.  Next time I try to start the bike down town all was dark again. Pushing and pressing the same thing didn't help this time, so I go to check the fuses, I took out the lower most one, it looked fine, put it back in and all lit up again. When I get home I experiment a bit and find that taking out that little black square didn't make the bike go dark ...so what happened his morning. What could be causing this. Is changing the fuse assembly a good idea or should the next move be something else?

[hairygit]

That little black block is the diode of the starter safety circuit. That would NOT cause the total electrical failiure you described. Pressing it probably moved a loose/dodgy connection elsewhere on the bracket/plate. If the fusebox wasn't cleaned/checked when the loom was changed, that will be prime suspect.

[taysidedragon]

Looking at the state of the regulator box and connectors I would check and clean the connectors and earthing points. Make sure battery connections are tight as well. You must have a loose or bad connection somewhere. Just be patient and methodical and work through them all. 👍

[Nurse Julie]

+1 with the above. That looks pretty rusty around the whole area and looks like it needs a good sorting out to fault find and prevent problems in the future.

[PatM]

Looking at the state of the regulator box and connectors I would check and clean the connectors and earthing points. Make sure battery connections are tight as well. You must have a loose or bad connection somewhere. Just be patient and methodical and work through them all. 👍

Someone critised some pictures i put on FB of my exhast mounts,in reply to a query 'what goes where, help please??'

 'Wow= your bike looks well-used!' comes back a reply...= Guilty as charged, the underside of my bike was and is a bit grubby, but im not putting it into a show!

My point is that electrics are not forgiving to rust/oxidisation and general age-related crud. Bullet-connectors were trouble when new and wet, let alone 40-years old,corroded and oxidised. You seriously need to have a bit of a tidy-up of the 'electrics' cupboard on your vintage Honda. They may be simple machines, but trust me- they are a git to solve electrical issues and will fox the Best on here from time to time.

The fuse-box simply unplugs and probably needs to be replaced - the spring-contacts loose thier springy-ness and the fuses- as Ive found out- crack internally or the 'solder' breaks. cary a packet of fags and it'll 'get yer home'. no, dont start up smoking as Id nver recommend that :-)

[Athame57]

I've been on the DSS site add to my shopping....

[Athame57]

Looking at the state of the regulator box and connectors I would check and clean the connectors and earthing points.

I just googled Regulator box for cb400f and got images of the finned regulator/rectifier I just replaced. Yet it's called a regulator in the manual..trying to find one on the web. DDS don't seem to have one.

[Bryanj]

They NEVER had the combined unit from Honda, only difference between 400 reg and all the othe 4's is the angle of the spade connectors

[Athame57]

They NEVER had the combined unit from Honda, only difference between 400 reg and all the othe 4's is the angle of the spade connectors

I'm not saying they did, I wouldn't know. But when I put 'regulator honda cb400f' into google all I get is the Rectifier I replaced (from DSS) ...I have to go to images to see the thing in the pic, they get called Regulator/rectifier there.....it isn't helping.

[taysidedragon]

You may not need to buy a new one.
Clean the spade connectors to get good electrical contacts. The box looks rusty but it's only a cover. The gubbins are inside. Check that there's no problem inside, if not just rub down the cover, repaint it
and replace. 

[Athame57]

Another black out early this morning thankfully just down the road from home. I've pulled open the fuse box and the first thing I do is order a new one from DSS. I find 5 Amp fuses where there is supposed to be 7 Amp fuses, and 20 Amp fuse where there is supposed to be a 15 Amp fuse, that's the fuse that blew and left a burn hole in the Fuse box assembly. But had there been a 15 Amp fuse surely it would have plane blown quicker? A fuse blows to stop worse happening does it not, so something somewhere is wrong? Bottom fuse holder is a bit loose.

[K2-K6]

Yes, you're right about the 20amp fuse.
The whole idea is that the fuse should be rated below the system it's supplying,  so that the fuse is the weakest component and by overheating it first then it will melt before the wires.

A dead short will usually pop the fuse out quite fast and potentially avoid melting the system at any point.  The combination of a fuse that was 33% above the designed rating and a resistance that has built up slowly would give that heat build up.  So it looks like the problem/resistance is consistently there and needs resolving.  It's possibly why someone has put a higher rate fuse in there,  and thought it fixed.  You'll need to identify this problem to fully correct it.

That starter solenoid in the picture looks pretty grimy,  there may be a route to problems there. It should also have both of the main current terminals covered by that insulator that's slipped down along the left hand wire.  I'd start with cleaning that and all the terminals there first,  then look for any similar details elsewhere as an initial clean up and look round the system to take out any very obvious problems.

[Athame57]

I've opted to get a new starter solenoid K2-K6, I've pulled apart and derusted the regulator/box , soaking some of those parts in white vinegar now! Thanks for this!

[Seabeowner]

The 15A fuse mounting is often seen overheated and melted, even with 15A fuse fitted. 40 year old tired and corroded contacts and soldered joint at the rear cause high resistance and heat.
Many replace with car type blade fuses.
Hondaman sells a replacement or you could have made your own.
http://sohc4shop.com/catalog/product_info.php?cPath=23&products_id=48

[Spenny62]

When my 400/4 went dark, it didn't take me long to work out why.  I wondered why it had half a roll of insulation tape wrapped round it.  I can't decide if this 'temporary' repair was inspired or just plain lazy!