Britbike forum Forums British Motorcycle specific Brands Bsa bulletin board +ve or -ve?

I am just about to wire my latest bike, yet another B441, and it occurred to me that I could wire it what ever polarity I wanted. Podronix regulator, Vape ignition.
I am inclined to stay with +ve "ground" just because, but is there any actual intrinsic value in doing so??

It is up to you. Whatever you are comfortable with.

I “offend” Lucas purists by going ve-, but in my day job, I deal with complex electrical systems that are ve-. Everything else I own with an automotive type electrical system, including my modern Triumph is ve-. So.....my vintage bikes are the same, simply to avoid having a senior moment and having an “oops” that would result in the smoke getting out of something expensive

Dave, I am just wiring up my A65 while waiting for stuff to come back from the plater, painter and candlestick maker. Much of my bike was destroyed by an electrical fire, caused (I think) by PO taking the fuse out of the circuit. Anyhoo, I was/am in a similar place to you and came to the conclusion that I could do whatever I liked with it. I went -ve earth.

Using a Podtronics rectifier and voltage regulator removed a whole bunch of circuitry and made the charging system very modular. Just 5 wires to connect. I also went the Pazon ignition route and adopted a single coil (not a problem you have) which again, made the ignition system very modular. Just 6 wires to connect.

I then built the rest of the wiring loom around the use of separately fused BOSH type relays. There is a separate relay for Ignition, Horn, Brake light, Hi beam, Lo beam, Left turn and Right turn. Seven relays in all, each with it's own fuse as well as a fuse from the battery to the relay bank. The handle bar controls just earth the appropriate relay, which then sends power to whatever the electrical component is. The advantage is that the handlebar control or ignition switch are not switching power. Just earthing a relay. If rain water gets in, you won't get a short circuit, like on the old Lucas stuff (ask me how I know). Instead, the headlight might come on, if it's not on already. All the lights are LED.

Very happy to publish the wiring diagram, if it helps.

Example of relays Here.
Fuses for battery and relays.
Lights on/off switch.
Headlamp.
And so on.. Happy to share any of it.

Steve.

the plus side of a power source is anodic, thats the physics. using positive ground turns the frame into an anode. I'm told thats the reason Brit cars & bikes had a ground wire system... all grounds went to wire rather than passing through the frame (big red wire, right?).. otherwise, current passing through the frame eventually eats the frame at the connections.

I'm for simplicity. negative ground, frame ground, main fuse at the battery, separate fuse on each circuit, relays for the headlight and (maybe) the horn. everything else direct off the switches

Neg Earth is convenient if you want to run LED lights as auto ones will fit.
If you want to get into the physics , the ignition system will be slightly
more efficient too. About a poofteenth better.

Can you explain the last bit, about more efficient ignition?

What's the functional difference between the upper circuit and the lower one ?



The upper circuit, if implemented on a motorcycle (as a handle bar light switch for example) is a wing and a prayer
away from rainwater shorting out the switch and blowing the fuse. If rainwater shorts out the switch in the lower one,
the light just turns on.

Presumably both circuits are wired negative ground and the salt water rain shorts both contacts of the switch to ground?
When I lived in wetter climates I frequently rode in the rain and never had it short out anything. Although once I was knocked over whilst crossing a flash flood stream, fully drowning the bike, and most of the switches did not work as well as the brakes due to the sand packed in everywhere but nothing shorted.

Yes, just added earths to the diagram for clarity.

The Lucas and Wipac switches on all my bikes leaked water and shorted out onto the handlebars in the rain, leaving you with a dead engine and blown fuse on the side of the road, hoping you remembered to bring a spare.

Hi,
Lucas "offended" them by doing that too ...

Either circuit, anything metal touches the battery +ve terminal and another part of the vehicle, the wiring from the negative terminal is literally toast in a few seconds.

One of these old heaps without an electric starter, put the single or main fuse in the battery "ground" wire, whichever it is.

Connections ... ime, wiser is either to waterproof them or not to submerge them ...

Now into my 44th year with the same Britbike; how long before this happens?

Regards,

Wait ......... you're supposed to fit fuses ?????

I ended up going for +ve ground as that is what my other B44 is . KISS. Saves thinking about which bike I am working on.

I think that water short circuiting your switches and blowing a fuse in a 12V system is defying the laws of physics.

And “eats the frame” at which connections? Where the component is connected to the frame or where the frame is connected to the battery?

Actually electricity flows, or arcs, more efficiently to the cooler of two electrodes. Since this is always the outer, or "Earth", electrode of a spark plug, positive "Earth" is marginally more efficient. Not of any consequence in a modern ignition system.
I have British bikes wired both common negative and common positive, they all work. Only reason I haven't changed the Trident is that the totally original system still works.

But that’s the high tension circuit. It doesn’t have to be same polarity or “flow” in the same direction as the 6V or 12V circuits on the bike.

So as I said earlier I stuck with +ve "ground". Oiled the bike up and gave it a kick ......... the damn thing literally fired first time! Ran and ticked over on the second !!!

Is there ant point in this post ...... not at all, just needed to tell someone!

That's great Dave. Well done.
Did you post any photos of it ?

I took some photos, and even a video, but they were both spoiled by some old fat guy sitting on the bike.

Yeah. An old fat, bald white guy keeps showing up in mine, too.