Honda CB400F Restoration Part 19 Electrics Testing Components & Reviving Wiring Loom

Added: 2026-05-09

[00:00:00]61 to 69 ohm.

[00:00:04]So let's have a look at the field coil.

[00:00:07]I don't hold much hope.

[00:00:11]Yeah. So it's quite a simple device really. Um I believe these are adjustable.

[00:00:18]Start at one end work way along. I might just wrap some as I go.

[00:00:52]Right. So, in this video, we're going to have a look at some electrics. Uh, yeah, we're going to have a look at the wiring loom.

[00:01:01]Um, and that needs some serious work doing. It's a right mess. Um, there's all sorts of dodgy connections like there is on here um on this little piece here uh to sort out and probably some new connectors and things. So yeah, that needs a lot of work. But before that, we'll just have a look at a couple of components. First one being the generator. Um, as you can see, I have already started to do some work on this. I've disconnected uh the the one and only wire that was connected. Uh yeah, these they were all in in some more um tape, but yeah, they weren't actually connecting. And you can see they're all there's another little point there, which is probably another connection that's failed. Yeah.

[00:02:02]And obviously this end is uh an equal mess.

[00:02:08]So yeah, what I'm going to do is put some fresh multistrand from these. I'll cut these sleeves right back, expose the solid copper core wire, and connect or resolder some fresh wires on. And I'm also going to make them longer so I can do away with these connectors here.

[00:02:36]There's another short little short um loom which would go from here up to the uh rectifier. So, what I think I'm going to do is just take wires direct up to the re rectifier.

[00:02:50]Um just to cut out some connectors, which I don't see are really necessary.

[00:02:57]Uh yeah, every connector is a possible cause of failure. So, the fewer the better. Uh yeah. So, what we'll do, let's just give these a little give these little coils a test.

[00:03:17]We can get this in here.

[00:03:19]Put this on the lowest ohms.

[00:03:27]So these should be between each coil should be 61 to 69 ohm.

[00:03:40]So we'll see what we got.

[00:03:44]We have still got some multi- strand here.

[00:03:56]08.

[00:04:11]So coils are all good.

[00:04:15]Reading not exactly between 61 and 69, but we're talking, you know, cheap multimeter here. So, uh, yeah, it's not that far out. I'm sure they're fine. So, that's that one.

[00:04:33]So, let's have a look at the field coil, which I'll have to got the dodgy connectors this end. So, this should be this should read between 4.6 and 5 ohm.

[00:04:58]4.6 4.5.

[00:05:03]That's probably dirty. Uh dirty contacts or these connectors, these connections here probably aren't very good. But yeah, looks like we're we're in the ballpark with that one as well.

[00:05:16]So that's that.

[00:05:20]Um I think Yeah, there's also some dodgy connectors, dodgy connections there coming up from the field coil. So, I don't think I will renew from here. This is all nicely potted. I'll leave that alone.

[00:05:41]Um, I'll probably just run some new wires from there. And again, I'll make them long enough or longer than standard.

[00:05:49]Right. So, um I mean if you're into your Hondas, you probably know how these work anyway, but for those that don't, I'll give a uh as best of explanation as I can. Um yeah, so these are static. Uh the only rotating part is the iron rotor which fixs to the fixes to the end of the crankshaft which um obviously when the engine is run that's spinning round.

[00:06:24]Uh so the field coil is energized by the regulator. When the battery asks or if you like when the battery asks for power, this kicks in and creates with the rotor an electromagnetic field which then obviously that's then energized and that this gener creates generates electricity.

[00:06:54]Um these three here. So this is three-phase AC generator.

[00:07:04]So these wires then go up to the rectifier gets converted from AC into DC and that then that then goes to the battery and then onto the regulator. So the regulator does the switching for this if you like um switches this in and out um as required.

[00:07:29]Yeah. Hope that makes sense.

[00:07:33]Does to me. Maybe not to you, but yeah.

[00:07:36]There we are. I've done my best.

[00:07:39]Right. So, yeah, I think we'll sort this one out first. Um, yes, we'll also have a little test of the rectifier um regulator. Can't test that until the engine is running. So yeah, can't really do much about that at the moment, but yeah, we can have a look at the the uh rectifier anyway, right? Let's have a look at this. Um, yeah, I don't hold much hope.

[00:08:13]Got more black tape around there.

[00:08:18]Um, yeah, it doesn't look that good in there.

[00:08:22]Bit of green copper corrosion in there. Right, I think I might have a little bit of a closer look at that. If we can actually get that apart.

[00:08:38]Be interesting to see what the layout is.

[00:08:42]Right, first of all, I'll just strip this back.

[00:08:48]Now, actually, it doesn't look like there's any damage to the actual wires. I think it was just this because it's so cracked and everything. Someone's just covered it up. So, uh yeah, I think that is junk.

[00:09:09]Which means I might just replace the rectifier and the regulator with a single unit uh rather than mug around cuz I don't know whether regulator is any good or not.

[00:09:36]It may be just as easy, just as well to replace the whole or replace both of them um with a single unit.

[00:09:46]Yeah, I think that's probably what we'll do. I don't think there's any really much hope for that.

[00:09:55]If you can actually uh would be nice to have a little look inside, wouldn't it?

[00:10:06]Does that come off there?

[00:10:09]Probably have to undo that.

[00:10:12]Yeah.

[00:10:17]Got a little spanner.

[00:10:22]It's not that size.

[00:10:25]Must be eight.

[00:10:28]Yeah.

[00:10:30]It's either got undo or shear.

[00:10:34]Bazard's junk. Anyway, go blime me. Yeah, that is pretty rusty.

[00:10:49]That is pretty rusty.

[00:10:53]That need to Yeah, that does, doesn't it?

[00:11:07]Let's get it in the vice.

[00:11:10]This might be destructive, right?

[00:11:30]There's plastic come off there.

[00:12:02]What we got?

[00:12:07]Might have to clean that up and have a little look.

[00:12:13]So, there should be six diodes in here, shouldn't I?

[00:12:18]Does that come off as well?

[00:12:22]Right. You see, I got the rectifier uh in in well, not exactly in bits. Just got the bag off it. Um yeah, I tested round the wires.

[00:12:35]Um and I wasn't getting anything. So, what you do is you test between each of these where the yellow wires come on. These bottom ones.

[00:12:47]Um, you test between each of those and the Which one is that? That's the battery positive and that's the earth. You test one way you should get a reading and the other way you shouldn't on continuity. You could do that between each one.

[00:13:07]But I wasn't getting anything.

[00:13:11]So because we had all that wrapped around there, I thought the wires don't look that good. So I just thought I'd try and get directly on the internal contacts, which means taking that off in the process.

[00:13:33]Yeah.

[00:13:35]broke that or sheared that off. The nut sheared off there. So, um, however, what we can do is now test this directly onto the unit. So, this is like your earth if you like on there.

[00:13:57]Uh you can see that there reading reading.

[00:14:15]So what was that one? 5 541 531 533.

[00:14:30]So all sort of roughly the same, right? And then between this connection here, which is the positive, you shouldn't get anything.

[00:14:51]which indeed we haven't. So, these um diodes are probably okay. It's either the joints have gone dry um for the wires or the wires are bad. I could test the wires, but yeah, one of these joints was bad. So, I think I'm probably just going to get a modern um unit to replace this and the um regulator.

[00:15:27]Uh yeah, I mean these probably are these when they start getting connections aren't good, they start getting hot, which that one may well have done. Or is that paint? Might be paint. Don't know.

[00:15:42]Yeah, they start getting hot and then they start to fail.

[00:15:48]So yeah, I think that's probably just as well to to replace it. So basically, that is junk, right? I thought we'd have a look at this while we're about it. Um, this is the regulator.

[00:16:04]So, I just removed the screws, the two screws that just hold this cap on and hold the sort of little protection plate, little cover for the resistor on the bottom.

[00:16:16]Um, let's just test that resistor while we're about it.

[00:16:30]Can't see that. Can you bring it in there?

[00:16:38]So about 9 ohm across there what it should be I don't know but yeah you're obviously getting something across it right so connections um so that would be the earth that is the output to the field coil and that one is your 12vt positive.

[00:17:14]Right? So 12 volt is coming in there going up to this top part of the points there and also it's connected to one end of the relay.

[00:17:42]Yeah. where this little wire here and the other end of the relay or coil is connected to ground.

[00:17:59]Right? So normal operation the positive will be coming straight in through that point through that point other this uh cuz this is normally closed going along and then out on the straight out to the field coil.

[00:18:26]So I assume when the battery doesn't need any more power, this relay comes into operation, pulls down that point and directs the output to the field coil through the winding here through the resistor. So it gets reduced amount of power.

[00:18:57]All right, we should be able to demonstrate that I think. Um let's see. I just hold these.

[00:19:09]Bring that in.

[00:19:12]I can just hold these on here and get a good connection on there.

[00:19:21]do this with two ends.

[00:19:25]Right.

[00:19:27]Let's see. We got 0.5 on there.

[00:19:36]Pull that down. Goes to 28 28.4 4 6.5 which is probably just the leads and the other bits of wire that are in the circuit.

[00:19:54]Yeah. So basically you get the higher resistance when that um relay is pulled in and that point is closed uh open sorry.

[00:20:11]So that's normally closed.

[00:20:13]That's open.

[00:20:16]Normally closed.

[00:20:19]Open.

[00:20:22]Yeah. So it's quite a simple device really. Um I believe these are adjustable there. Probably just the height of that I would assume.

[00:20:36]Slacken that off and raise or lower this.

[00:20:43]Yeah, I would think.

[00:20:52]Yeah, quite a simple little device, but like I say, we're not going to use it because we're going to go solid state.

[00:21:02]Yeah, bit more reliable.

[00:21:06]Although that would probably still work.

[00:21:10]Right. Okay. Well, we'll put that back together. We will keep it cuz you never know.

[00:22:05]Right, wires attached. Heat shrink on. I've just now got to I'll probably put another bit of heat shrink over actually just to group all them together.

[00:22:18]And then I've just got to tie them all back into here. I probably just use some um cable ties.

[00:22:26]Yeah. Um so I think that'll be okay. And then obviously another bit of sleeve and over another bit of heat shrink over.

[00:22:32]And uh yeah, that's my little very handy miniature heat gun if you like for um it's actually a desoldering thing, but it's really good for um really good for uh heat shrink when you want to get into rather than having a great big, you know, heat heat gun on there, you can get in with the little tip on there. Get right in close and direct the heat where you need it.

[00:23:11]Right. So, I need to just tidy this up.

[00:23:16]Get those tied in and then uh we'll have a look at the other coil.

[00:23:24]Yeah, I don't quite know what to do with this one now. Whether I might have to actually see if I can Um, get under there. Get this off that.

[00:23:40]See here?

[00:23:42]These wires have been quite compressed, badly compressed by this little metal strap that sort of holds them down.

[00:23:54]Um, I might just cut them back here and bear the wires and do my connections there.

[00:24:04]And uh yeah, maybe cut this tab piece off completely and put heat shrink right over there to cover this whole thing and use the heat shrink gripped against there rather than using this metal tang as Yeah, that's quite badly squashed. Yeah. So, I mean, the connections are only under here, but I don't really want to disturb that, unless I have to.

[00:24:42]Right.

[00:24:43]I'll see what we can do with that.

[00:24:48]Well, in the end, I did just chip away at that uh resin and uh have liberated those wires. Uh yeah, so I can put fresh ones on. These are these have gone really hard.

[00:25:06]Um plus they're squashed and all sort of damage is under there. And the other thing is they're aluminium by the looks of it, which is uh not good unless they're kilted copper, but aluminum does fatigue. Maybe copper actually underneath there.

[00:25:39]It could be. Yep. So, I can now make my connection right back here with my new wires.

[00:25:52]There's that one done. I've just tested it. It still tests. Okay. So, yeah. So, we just new wires on there direct onto the solid winding or the ends. Uh, I cut that metal tang off.

[00:26:10]Just left the metal base piece sticking out. Put a bit piece of heat shrink around that cable tie.

[00:26:21]Yeah. And heat shrink on this as well.

[00:26:23]So, yeah, I think we'll be okay there.

[00:26:26]Right now, we'll have a look at the main wiring loom.

[00:26:34]Let's just raise this up a bit. You can see the full state of the mess.

[00:26:42]Yeah. So, we got all sorts of insulating tape all wrapped around there.

[00:26:53]So, I think what I'll do is I'll get all the and all over there. I think I'll get all the insulating tape sticky mess off first.

[00:27:03]And we'll sort of uh inspect wires we as we go in that one there straight away.

[00:27:15]Got bare wires in there. So that'll need re terminating.

[00:27:22]All this is just falling off. That can just be rewrapped.

[00:27:31]I think that's for the little um diode, isn't it?

[00:27:39]Yeah. So, we can I've got reels of cloth tape. I've got loads more than this. Um yeah, so we got plenty of that.

[00:27:48]Uh, you know, normally if I was doing a Warren loom, I would use um heat shrink, but as with I'm not wanting to disturb anything unless I have to like the ends. Can't really get um heat shrink over there.

[00:28:09]So, it's going to have to be wrapped.

[00:28:11]Uh yeah, again, we got more bare wires there.

[00:28:17]That is probably a broken connector. Is it?

[00:28:27]No. Just got a It's got damaged wires for some reason.

[00:28:32]Yeah. So, like I say, I'll strip all this um horrible stuff off.

[00:28:38]Multiple layers of insulating tape and we'll just rewrap the whole thing. I think be the best thing to do.

[00:28:47]Yeah, this is all I think this is actually Yeah, that's original. That is looks of that all just come apart.

[00:28:59]Yeah. And then actually obviously if that's all off, we can actually inspect the wires underneath. make sure we've got no um you know like that any little breaks in the insulation, anything like that. So I think probably start at one end, work my way along. I might just wrap some as I go so I just don't end up with a mess of wires.

[00:29:29]Yeah.

[00:29:31]So, like this one here.

[00:29:34]Just do that one first.

[00:29:36]Um, tidy that up and then we'll have a look at that piece.

[00:29:45]Cable tie on there.

[00:29:50]Yeah. I mean, it's just a mess, is it really? Right, let's get on with it. Um, yeah, I won't go through this in too much detail unless I find something interesting.

[00:30:02]Just uh blue crimps. Yeah.

[00:30:12]Try and work out what's meant to be on that.

[00:30:16]Yeah.

[00:30:18]Broken wires under there. Looks cut wires. Yeah, that's going to be a bit of a challenge. It's going to take a long time. There's probably not much interest for the video wise.

[00:30:31]So, um yeah, a lot of this I won't record, like I say, unless I come across something interesting.

[00:30:39]Right, I will get on with this.

[00:30:45]We've got this down the original black PVC covering.

[00:30:51]Um, yeah, there was some I think that was gaffa tape actually over the top of that and some insulation tape. Um, yeah, I don't know if these are factory or not.

[00:31:03]These little connections here. So, we'll we'll just have a look at them. And uh, got the end.

[00:31:11]Always easy to find the end, is it?

[00:31:18]Yeah. Not sure if they're factory or um could be, I suppose. Seems a bit um bodgegy just putting insulating tape around them. But yeah, think I'll just um I will just re redo these. take the old tape off and put some fresh on, I think.

[00:31:45]Yeah. Um, yeah, I've just taken this big boot off these ones just to make it easier to work.

[00:32:01]Just give them a little bit of a clean up with some carb spray these wires cuz they are a bit groy.

[00:32:09]Uh, yeah. Yeah. So, this one I've got to repair.

[00:32:15]Let's see if I can take that back and do the repair in here somewhere.

[00:32:22]Just got that clumped together with a bit of tape for now. Same with these ones here.

[00:32:29]Just put a bit of temporary tape around just to hold them in position so I don't lose where the they're meant to come out.

[00:32:37]Yeah.

[00:32:39]And I've just got this clamped down between a couple of um clamps.

[00:32:48]Just makes it easier to work. Sort of stretch it between the two especially when you come rewrap.

[00:32:54]Um yeah, just makes it a bit easier to do.

[00:32:59]Yeah, made a start. Anyway, well, there we are. But once I stripped all that back, we got wire twisted together there.

[00:33:13]That was sort of twisted together.

[00:33:16]Um, yeah, that was Don't know why that was just cut like that. That one had two wires on it going to one terminal. I think they just found something and used it. that was obviously damaged at that point that wire.

[00:33:39]So that is uh green with a yellow stripe and black that has got to be front brake switch.

[00:33:53]Yeah, that's what that is. Right. So yeah, there's one to repair start. And I think if I just do the same length as that, I won't be far out. I just need to find out what terminals are meant to be on the end.

[00:34:09]Yeah, that's the first little repair to do. But I should be able to get some heat shrink over that anyway for that one. So, that'll be good.

[00:34:22]Well, unfortunately this wire, as you can see, it has got black corrosion on it, uh, or oxidization.

[00:34:32]Um, and it won't take solder. I've even put some flux, extra flux on. It just won't take. So, um, what I'm going to have to do is like with this one, just going to have to crimp on couple of connectors. And then when we come to put it on the bike and connect up to the, uh, the switch, I'll just run a couple of these up to these that I'm going to fit.

[00:34:59]Um, yeah. So, what I just been doing is just clean this back with a bit of uh I think this is thousand grit. So you have to kind of get as much of that off as possible.

[00:35:14]And even doing this, the solder wouldn't take. It just wasn't interested.

[00:35:24]Yeah. So I'll do the same with this one.

[00:35:26]Got another connector there to put on. So, yeah, first little problem really.

[00:35:36]But, um, yeah, one of those things. I've had this before with with old wires.

[00:35:44]You just they just don't for some reason won't take the solder.

[00:35:50]I'm pretty sure that is copper.

[00:35:55]um you know modern modern wire and you know can't be quite sure what it is but this stuff from the ' 70s I'm pretty sure that's um that's proper copper yeah I worked for um worked in the telecom industry um they went through a time where because of the price of copper they were replacing or instead of using copper they were using aluminium um wires and what a disaster that turned out to be as um you get a little bit of movement and it just fractures.

[00:36:50]Terrible stuff. So yeah, and it's really hard to repair. You can Well, you can go out there one day, do a repair, and you might be back the next week doing the same repair on the same bit of cable.

[00:37:04]It's just Yeah. It's awful stuff. Awful.

[00:37:07]Yeah. So, that turned out to be a little bit of a um bad decision. Really didn't turn out to be very economic in the end. May have been at the time, but not in the end.

[00:37:20]Yeah.

[00:37:22]Uh right. So I'll carry on. Right.

[00:37:26]Carrying on with this uh wiring loom. Um in here this uh where is it?

[00:37:40]One of these connectors.

[00:37:42]The insulation gone on that wire. So I cut it back. I didn't have any of these sort of quad connectors.

[00:37:52]So, I've just put two split the wire and put two of these on. So, I've got the same amount of connections.

[00:38:02]Sorted that out.

[00:38:04]Uh this connector, the wire was damaged again on the insulation into there. I haven't got any of these. I've got some on order. the little internal ones for this. So, I've just ran a new wire back to where the sort of main connection for all these black wires is.

[00:38:27]Yeah. So, I've done that. I've covered this. I've put a layer over there. I'll probably once I've done the whole thing with this this stuff, I'll probably give it another another going over the whole thing because this stuff isn't particularly good quality. Not as good as this, but this is only thin stuff. I'm just using this to tie in where I need to. Um, yeah. So, I've sort of got that piece partially done.

[00:39:04]Um, so I now started stripping back all this here.

[00:39:15]So what I'll do now, I'll now wrap that just to keep that all together because this here needs quite a bit of work and there's a lot of um yeah, a lot of leads here go into one point. So yeah, I need to keep this together. But before that, I need to sort this wire out. Got a damaged wire there. So again, I'll need to take that back or run a new wire from this little bundle here.

[00:39:45]Little bundle of uh Well, that's going to be earths, isn't it? Green. Yeah.

[00:39:51]Yeah. Yes. So, I've got to try and keep this together and um do that repair and then I'll wrap um yeah, rewrap all that lot and then have a go at this all these all these ends here. They all need to be redone. Yeah. So, I'll just try and keep that all together for the moment while I sort this out.

[00:40:18]Right. Got these mostly free of the old tape.

[00:40:24]Just got little bit on that left to do that one. Uh that's that piece of wire which was damaged.

[00:40:37]Not sure how long this is meant to be or what it's meant to be for.

[00:40:43]Possibly frame earth. So I'm just going to leave that.

[00:40:48]um as long as I can for now. Uh I won't put an end on it or anything.

[00:40:56]I'll wait on the bike and then I can just cut that to end uh to length and uh and put a if it is frame earth, put an eyelet on. Uh yeah, so basically I'm nearly at a stage where I can start rewrapping all these.

[00:41:12]Um, yeah. So, I think I'll just start I'll wind them back to this point here. Do them all. Wrap them all back to there. And then that can be um let's see if I do them all apart from this one. I can then wrap along and then finish off tying all those in. I think that'll be the way I do that.

[00:41:42]Yeah, I just need to check with the warren diagram what this one is meant for. Uh whether it is meant to be just on its own like that or not. Yeah. Once I've done that, I can then start uh tying everything in.

[00:41:57]Yeah. So, that's uh nearly there.

[00:42:07]There we are.

[00:42:09]That is All that end done.

[00:42:14]I've just been doing a 50% overwrap and then I've gone all the way along this main loom there. I've just double wrapped that.

[00:42:28]So, it's had two layers. Um, yeah, I think that'll be okay. Um, just got this last little bit up this end to do this termination here.

[00:42:43]But yeah, apart from that, that is just about ready to fit once I've done that last little bit.

[00:42:58]Yeah, I think that looks a whole lot better than it did. Uh, did they just have to put a couple of new sleeves over those ones there? They just had a bit of black tape round. So, I just put some new sleeves. Um, this isn't dirt. This is just This is black paint.

[00:43:22]Yeah. So, that won't really clean off very well.

[00:43:26]But, uh Oh, that one. Have I got to do Oh, yeah. I've got to do that in there.

[00:43:32]Just need to depin that.

[00:43:36]So, once I get the um the connectors for the other end, I'll do this one as well.

[00:43:44]Yeah, I forgot about that one. I think all the others are okay.

[00:43:50]They just need a bit of a clean down with some um contact cleaner.

[00:43:58]But uh yeah, I think that will do the job. Um yeah, so the next thing will be to get it on here.

[00:44:18]Yeah, I have got a diagram somewhere of um the routing.

[00:44:25]I did get the little bit which goes over here, the little cable sort of standoff thing.

[00:44:35]So, I've got that to go on.

[00:44:40]Yeah. So, next video I will probably show that already on um just show the rooting of it.

[00:44:48]Uh yeah, and bars. I'll do them in the next video as well, I think.

[00:44:58]Get the bars done. Get the wires fed for the controls for them.

[00:45:04]Those on uh rear mud guard I haven't got yet. Well, I've got one, but it's really bad condition.

[00:45:15]I have got a new front mud guard which yeah might do that in the next video as well. We'll just fit it and show it show on.

[00:45:24]Yeah. So, it's coming along.

[00:45:27]Um Oh, yeah. And I did get a cover for that. That is actually a 3D printed one. Got that off eBay.

[00:45:43]I think it was about 10. I went a lot of money.

[00:45:47]Certainly a lot newer than trying to find a new old stock one. I don't know if that's supposed to be a tight fit on there or what. But yeah, whether it's supposed to be something clamp that on. Don't know.

[00:46:03]Yeah. But uh at least we got something on there.

[00:46:09]One piece I have been looking for is the little steel tube which comes off there.

[00:46:19]Haven't yet sourced that.

[00:46:24]But uh yeah, these bits you keep looking for that. Uh yeah, it'll turn up eventually.

[00:46:33]Yeah. Right. So I think yeah, that'll be it for this video.

[00:46:40]Uh yeah. So, please um comment if there's anything you can think of that I've missed.

[00:46:50]Uh yeah, please like and subscribe.

[00:46:54]Don't get many views.

[00:46:56]would like to increase my views, but uh yeah, it's one of these YouTube al algorithms that you don't really get promoted unless you get a lot of comments and a lot of likes and all that sort of nonsense.

[00:47:09]So, yeah, would be good.

[00:47:16]Well, there we are.

[00:47:18]We'll see you in the next one.