Topic: Can someone double check this wire diagram

[q2418130103p]

This is the wire harness I plan to build for my CB550.

Can someone take a look at it, see if I am missing anything, or offer suggestions on things to change.

Notes: No starter, no signals, taillight on when key is on, momentary kill switch, relay for main power, separate fuse for main power and accessory power.

[number13]

I think that kill switch to the coils is going to
arc a lot. You may want to interrupt the
ground in that circuit.

[Kevin400F]

You need to show two sets of points, and separate the "blue" and "yellow" wires from the individual coils to the separate points sets.

Also, I would not recommend a momentary kill switch, which by definition would only interrupt the ignition power when pressed (against spring tension).  Use the factory kill switch or something that functions in an equivalent manner.

[KingCustomCycles.com]

Comparable to this one, many have been wired this way successfully:

[Bodi]

Looks pretty good. You'll want a horn switch, and you've shown the kill switch as press-to-run: OK if you want that but what if you need to scratch your ba... nose?
Really the kill switch needs to be on/off, not momentary. When you need it, you may not want to hold a button down while attending to whatever emergency has required its use. The kill switch has to carry about 5 amps reactive load, you need a pretty beefy switch. Putting a diode backwards across the kill switch and relay contacts will reduce arcing and extend contact life a lot.
I assume you want to use a non-automotive key switch so you added the relay. If you use an automotive one it will easily handle the full system power and you can lose the relay.
You have to use high-flex wire in bike harnesses. The vibration will eventually work harden normal hookup wire in odd spots through the harness, and the flexing of wires through the steering will do it very rapidly. Work hardened copper is very brittle and will break easily with further bending.

[Kong]

You red wire from the rectifier to the battery should be moved to the fused side of the output line on the battery.  Just as a second comment you could put a relay in there where you have your kill switch and then have the actual kill switch simply interrupt control power to the relay. it would allow a lower amp draw through the kill switch letting it last forever and also let you have a cleaner power supply to your coils, something that is always welcome.

[Kevin400F]

Factory wiring arrangement has the red wire from the rectifier directly to the positive side of hte battery, not through a fuse.  Your diagram is OK in that respect.

[Kong]

Factory wiring arrangement has the red wire from the rectifier directly to the positive side of hte battery, not through a fuse.  Your diagram is OK in that respect.

Would you do it that way?  My own belief is that if its hot it should be fused at the earliest possible convenience.  Remember, the fuse is there to protect the wire, not the device, and the way it is now - factory or not - that hot wire is unprotected.  I'd fix that.

[Kevin400F]

The reason the red wire from the rectifier to the battery is NOT fused by the factory is that it needs to carry whatever charging current is necessary, depending on the circumstance (low battery, high draw, or both).  I don't think the Honda engineers were ignorant.  They wired it direct for a reason. 

[Kong]

A well installed fuse won't make any sort of important drop in voltage and I have to ask are you telling me that because Honda did it 30 years ago it can't be improved on?  From what it looks like to me the guy is trying to build his own wiring harness, presumably to improve on the most excellent web Honda produced.  If he wanted to do it the way the all-knowledgable engineers at Honda did it he could dump $50 on a used harness from E-bay and not waste his time asking for advice here.  If the guy's asking my advice he'll fuse that line to protect it, if he wants to listen to you he can leave it like it is.  His choice and we'll all walk away happy.

[Kevin400F]

What amperage fuse do you recommend?

[q2418130103p]

Yeah, I drew the kill switch in the N.O. position, I figured it would be easier to tell it was a switch like that.

Bodi, I didn't realize that the automotive keys were so good.  I was planning on reusing the factory switch.  So I suppose I can get rid of the relay.

You guys are probably right though, I should probably change from a momentary to a toggle of some kind.  I am used to dirt bikes which has a momentary kill button.  I will poke around some bike electronics sites and see if I can find a nice looking headlamp/kill assembly.

Normally not having the link between the rectifier and the battery fused would bother me.  But I plan on having to two devices within 6 inches of each other.  If I end up moving the two items further apart then I will probably fuse it.

The rectangle with the word 'HORN' in it was the horn switch, for some reason I didnt draw it as a switch... Not sure why I did that.

Kevin400F, I'll go ahead and make the change to the points wires.

KingCustom, I used that diagram for reference, I should have referenced it in my post.  Sorry about that.



This diagram is for a very minimal harness I am making for my cafe.  All the electronics will be under the seat.  I will be replacing the factory controls with some after-market ones that are a little slimmer (suggestions would be appreciated for switch suppliers).

Thanks for the help guys, I am looking forward to any other input you all have.

[q2418130103p]

Can anyone recommend places to get generic motorcycle handlebar switches?  I have only found a couple sites, and the selection is limited.

I would like to put at least the kill and headlights on the right hand side, maybe the horn as well.  The horn could go on the left I suppose.

[TwoTired]

The diagram wrt the fuse is correct as shown in the diagram.  Do NOT move the wire downside the fuse away from the battery.  The fuse is indiscriminant about which way the current is flowing.  Further, the circuit from rectifier to bike load would be Un-fused entirely  That leaves the wiring and bike loads exposed to 18 amps from alternator plus 15 amps from the battery with NO protection at all (assuming a 15 amp fuse is used).  A 33 amp short will usually fry something.

If the battery is low and the bike loads light, a 15 amp fuse is near blowing just with the charging current from rectifier to battery.

The Honda engineers got the wiring right as they usually do.

If you want to fuse the charging system from the battery, then add a separate fuse for it and make it about 30 amps.  But, as long as the rectifier is healthy and you can refrain from hooking up a battery backwards to it, it doesn't need a fuse and the resultant voltage drop losses that it adds to the circuit.

Cheers,

[HondaMan]

The reason the red wire from the rectifier to the battery is NOT fused by the factory is that it needs to carry whatever charging current is necessary, depending on the circumstance (low battery, high draw, or both).  I don't think the Honda engineers were ignorant.  They wired it direct for a reason. 

You're right: the direct wiring has several features:
1. Having the rectifier always connected to the battery in this manner damps the 33 volt peaks that otherwise would hit the bike's bulbs (and fry them all) if a fuse between the rectifer and the battery were to open up. In automotive parlance, this is called the "alternator dump scenario" where the load is suddenly removed and the regulator cannot shut down quickly enough. Over-the-road truckers, who add extra alternators with a cut-out relay, often suffer from this method...on these bikes, a poor (+) terminal connection at the battery achieves the same bulb failures.
2. The wire between the rectifier and the battery on these bikes is about 14 AWG size. This can carry 30 amps with nothing more than a heated wire jacket (turns it brownish) to show for it.
3. When the regulators fail on these bikes (usually due to a broken resistor on the back) the charge goes to full 13 amps or so, permanently. If a 15 amp fuse were used in line with the battery and it dried out, the battery would go to a short and blow that fuse, then blowing all the bulbs (see #1).