Can someone explain the difference between negative and positive ground?

[Patches]

OK, so I know this is not XS650 related but maybe someone else can learn from reading this too. I just picked up a 1972 BSA Lightning. I got a great deal on the little bike. It has several upgrades like Boyer Ignigion and a Mighty Max Reg/Rec with built in capacitor (I believe). I did a little research and I guess the Mighty Max allows for a negative ground...? Which I believe should be to the battery. From what it looks like this was not what these British bikes usually had. I guess they had a negative ground from the factory, but I'm not sure what that means....?

Can someone put this into motorcycle terms for me?

I believe the wires coming off of the alternator are AC current so it doesn't matter how you hook them up. But apparently the Mighty Max converts them to DC, thus the need for a dedicated positive and negative wire to the battery....?

I guess the Boyer can be wired up for either a positive or negative ground, but wouldn't you just hook it up to negative (on battery) and 12V when the key is on?

I have a ton of XS's, but this British thing is new to me. The bike is really neat, but it will need to be completely rewired due to the PO.

Any help is appreciated, I'm not a member of any other bike forums, but I have a feeling I may have to find a BSA one for this project. Any recommendations?

Also, pics to follow!

 

[azman857]

Basicly its the positive terminal of the battery connected to the ground (frame) instead of the negititve post. Look at the ground as being the common return path to the power sourse to complete the curcuit.

 

[donald]

Your BSA was definitly a positve ground system when it was new google British cycle supply they should be able to supply parts & service manuals for most British bikes

 

[Patches]

^ ok, I get that.

And so where would the negative connect to?

Since I have the Boyer and mighty max has the bike been changed to where I need to ground the negative?

Thanks for the help so far. Maybe I'm just dense....

 

[azman857]

The Negitive post is now the power supply. It would be connected to the fuses and ignition switch.

 

[tonyc]

I have a1963 BSA A-65 and it was originally positive ground until I changed it.

 

[DirtyErnie]

only real difference... a positive-grounded machine will corrode away faster.

 

[donald]

I have a1963 BSA A-65 and it was originally positive ground until I changed it.

What all did you do to change it from positive to negative ground

 

[tonyc]

I was re-wiring my bike so I just wired it negative ground. My bike was originally 6-volts and I changed to 12 volts.

 

[Patches]

I was re-wiring my bike so I just wired it negative ground. My bike was originally 6-volts and I changed to 12 volts.

Yep, this thing is a mess in terms of wiring and I'm just debating a complete rewire. Really, it shouldn't be too hard.

 

[donald]

I was re-wiring my bike so I just wired it negative ground. My bike was originally 6-volts and I changed to 12 volts.

What did you use for an alternator and how did you get around reversing polarity through the rectifier and the zenor diode

 

[tonyc]

I put a newer 12 volt alternator on it could be either 12 or 6 volt AC until you send to rectifier and regulator. I used a Boyer and Boyer box Zenor and rectifier together.

 

[hotdog]

Ahhh the British & their + earth stuff...funny little chaps...all you need now Patches is a early series Land Rover to haul it in...ha ha

 

[tonyc]

I did have two Rover cars!

 

[wesleyonoel]

British weren't the only ones to use positive ground electrics. My '51 Ford Crestliner has a 6 volt positive ground system - stock! I think some older Ford tractors might be positive ground as well.......................Wesley

 

[Pure-Pork]

British weren't the only ones to use positive ground electrics. My '51 Ford Crestliner has a 6 volt positive ground system - stock! I think some older Ford tractors might be positive ground as well.......................Wesley

My N9 ford tractor has positive ground, but I'm about to replace the 6 volt gen system with a 12 v alternator/coil kit.

 

[Patches]

After some R&R (reading and research) I'm on top of it. Being that the bike's wiring is in a state of disrepair I'm going to convert it to a negative ground, basically for ease of maintenance and ability to add newer electrical components.

This bike has the OIF (oil in frame) and the frame was just repowdercoated last year. I really like the look of the OIF, and I think this will be a great restomod cafe racer being that too many components are missing for a restoration. The wheels are really cool and in great shape. The BSA tank was replaced with a perfect Triumph Bonneville tank, and apparently the PO had it running but just for a sec.

A guy down the street from me has a chopper shop. He specialized in shovel heads, but he has had a couple Triumphs in the past and has some of the speciality tools (for finding TDC and valve adjustment).

This should be a good learning experience.

Now if I could just some of these other projects out of the way.....

 

[donald]

I put a newer 12 volt alternator on it could be either 12 or 6 volt AC until you send to rectifier and regulator. I used a Boyer and Boyer box Zenor and rectifier together.

Walridge Motors Ltd in Canada sells the boyer bransden power box they also have another system called a Podtronics-power module which does the same thing allowing ei ther + or - ground .It was about half the price of the Boyer system.

 

[donald]

Ahhh the British & their + earth stuff...funny little chaps...all you need now Patches is a early series Land Rover to haul it in...ha ha

I was told that brits drink warm beer because their fridges are made by Lucas the British prince of darkness

 

[blim840]

Hello , I rewired a T140 the other day and its easy you just have to forget that your wiring the battery round the wrong way if that makes sense , you are switching negative not positive and your fuse is on the negative side ! I only had the instructions for the boyer box for an xs but it didn't work straight off , i got the the feed to the box to the wrong wire , the xs it woud power up the red wire with the coils but on posotive earth you need to power up the white wire , luckily for me boyer box's are strong and we wired it right and off it went , my friend who's bike it is was telling me to wire it negative earth you just need to change the zener diode but don't quote me and thats irrelivant with your mighty max thingy , do they have a web site , they may tell you how to convert it to negative earth ! also if in doubt check out the boyer web site as they have wiring diagrams and tech info , and bin the standard 6v coils (if this is what its running) and go for a dyna coil or something , again check out the boyer site for details of impedence for your particular box , as long as its a pretty close match (+/- 20% but in reality you can go more) it should work fine !