Topic: CB400F Wiring and Sanity Check

[monstergarage]

I'm going to be building a wiring harness from scratch, most of the old electrical system either didn't work, was hacked on by the previous owner (thanks for that, seriously learn how to use a soldering iron and some common sense!  ), or I'm removing. I modified a diagram I found on the internet with everything I plan on doing when building the new wiring harness. Just need a sanity check before I start wiring over the weekend, its not the first time I've built a wiring harness from scratch, but everyone makes a mistake once in a while (buying this bike for one  )

I will be removing the tach/speedo/indicator cluster, blinkers, starting system, regulator, rectifier, and fuse block...most of which does not work

I have this rectifier regulator, I have no idea if its crap or not, but it's what I have:

http://www.ebay.com/itm/Voltage-Rectifier-Regulator-Fits-Honda-CB-400cc-CB-500cc-CB-550cc-CB-750cc-/321903175134?fits=Make%3AHonda&hash=item4af2eca5de:g:PywAAOSw14xWLYX8

For indicator lights (neutral, highbeam, oil pressure) I have these:

http://www.ebay.com/itm/322069383963

Have a new generic fuse block.

Have an 80's style front break master cylinder with an integrated brake light switch (whole front brake system deteriorated)

http://www.ebay.com/itm/80s-Style-Black-Brake-Master-Cylinder-Honda-CM400-CM450-CX500-CB650-CB750-/181969165141?hash=item2a5e351b55:g:ou0AAOSw1S9WeHZG

A complete wiring kit, new connectors, hand controls, battery, etc. Basicly, if its electrical its new except the alternator and coils. I was also thinking of adding an LED indicator for ignition on and tying it into the tail light since its on for both positions on the ignition switch (not in the picture). And a cheap bike computer to use as a speedometer some time in the future. I pretty much have all my bases set, I even have blinkers if I decided to use them.

I would like to have a working starting system, but I'll address that down the road.

[monstergarage]

Fixed photoshop mistakes and added the on light that ties into the tail light I was talking about

[calj737]

The only reason that diagram won't work is if you mess it up the installation.  But I do not see a Turn Signal Flasher as part of the diagram, and if you do opt to use your indicators, one will need to be factored in.

[MoMo]

10 to 15 minutes to install new harness,  who knows how long to make one....Larry

[scottly]

That master cylinder has a 5/8" (15.8 mm) piston, which is much too large for a single disc 400. The stock MC is 14 mm, and you might even want to try as small as 12mm.

[Brian G]

I see also that the rectifier/regulator illustrated has only two (black and white) wires for the regulator connections in the harness but my new harness has an additional green (ground) connector. I was about to purchase an alternative rectifier/regulator specified as being for the 400 which has the three wire connections for more than twice the price but if the two wire unit will do the trick... Would it ground through the housing instead of the harness, perhaps?

Thanks and Regards,

[Tim2005]

That harness design is going to put quite a load on the red wire & it's fuse, with the lights, coils, alternator etc all being powered though one fuse & wire. Make sure you use substantial components, including a key switch that's designed for that continuous load.

[monstergarage]

It has a CB750 front end and brakes

[monstergarage]

But that's no fun 

[monstergarage]

Maybe you didn't examine the picture close enough? The rectifier regulator has a positive that goes straight to the battery (red) and one that is only hot in run (black wire)

[scottly]

It has a CB750 front end and brakes

What year 750 front end? Even with dual rotors and calipers, the 5/8" master is too large for most of the 750s. Just how did you fit the 750 front to a 400??

[calj737]

That harness design is going to put quite a load on the red wire & it's fuse, with the lights, coils, alternator etc all being powered though one fuse & wire. Make sure you use substantial components, including a key switch that's designed for that continuous load.

Maybe you didn't examine the picture close enough? The rectifier regulator has a positive that goes straight to the battery (red) and one that is only hot in run (black wire)

I think Tim's comment has more to do with the fact that you're only running a single fuse from battery + to key on RED. Most CBs after '73 split their load across 3 or more fused circuits (TAIL and LIGHT and MAIN). If you stay with a single fuse, make sure its rated high enough for the load, and that your key switch is too. Aftermarket switches (Emgo brand especially) aren't rated for the load and fail rather frequently and quickly. A relay before the switch helps a lot. 

[Bodi]

I have to agree with the points about using a single fuse and amp rating of the Emgo type switch. The OEM switch was marginal in my opinion, the aftermarket ones are less robust.
I can see you want a super simple wiring harness but adding a main power relay and an additional fuse can increase reliability.
I have had fuses blow at night on a highway. It's spooky when the lights go out but shorts staining when the engine cuts out as well. Having one fuse means the latter. Fuses can blow just because a bulb burns out (and they will) if the failed filament drops across the internal power stalks.
One main fuse or circuit breaker - 20A or so - on the battery feed to the harness will provide overall protection so a short doesn't start your bike on fire.
Adding a simple automotive relay that operates from the switch black wire and connects battery + to the harness black wire saves that keyswitch from rapid failure. Putting two 10A load fuses after the relay, one for the ignition and one for everything else, isolates your ignition from the lighting etc., and the 10s should blow before the 20 if something goes wrong. Yes it's a few more wires and connections but you only have to do it once (hopefully!).
Make sure you use high flex wire for your harness. Auto store general purpose hook-up wire is too stiff for the steering head area and will work harden and break after a while from the flexing.

[monstergarage]

It came with the 750 front end, but was poorly installed by the PO, I got an adapter kit from All Balls, came with the spacers, bearing races, and of course bearings. The forks are just a bit too long, besides that it works great. I'll have to check to see how the master cylinder works

[monstergarage]

Oh okay, I have a fuse block, I have an even more up to date model that includes fuses, most wiring diagrams on the internet seem to neglect them.

[monstergarage]

Is this a step in the right direction? Added fuses, headlight goes through fuses and relays directly to the battery, all the lights are LEDs except the headlight, so they don't have a high draw. Do the coils need a relay or maybe a relay right after the ignition switch to remove almost all power coming from the ignition?

[calj737]

Coils don't need a fuse. Better to have the relay before the key switch to lighten its load. Running your LIGHT and TAIL through those fuses (even though LED) always add reliability.