Keeping The Rockers Rolling: '70 BSA Lightning Electrical Overhaul & Upgrades

My 1970 BSA Lightning presented me with many learning opportunities during the past summer as you are aware of if you have been following my foibles. The year started with electrical issues and ended with carburetor issues (I think). While I found many issues with my 46 year old wiring, big surprise, I was able to get it mostly ironed out. I still have a miss after 5K RPM which I think is carb related. Although I had the wiring sorted out the harness was pretty rough. It had been cut and tapped into by a previous owner and had the issues you would expect from wiring of that vintage. The Hornet I rewired has run great, and wanting to replicate that success, I decided to build my own harness for the Lightning. So here I go....more modern bits....a new wiring diagram.....a fuse box....a lot of time on my hands during this Michigan winter.....

The old bits on their way to storage.

New bits and brackets. A Lucas high output single phase alternator and a Trispark ignition already reside in the Beezer.

My first order of business was to decide what to keep and what to put away. I already had a Trispark ignition, Lucas high output single phase alternator, Podtronics regulator, and an LED headlight (blown and in need of replacing).

Upgrades:

Make a new wiring diagram and harness
Negative ground (It's a US thing & the LED hi & lo beams will work - no arguments please)
Battery free system
Kill button (I always wondered why they stopped putting these on)
Bosch 12V horn and kill switch relays
Trispark dual lead coil
Marine grade 25 amp toggle on-off switch
Fuse box
12V power port
Custom brackets to hold the new bits
Lucas connectors. Crimp for blade and solder for bullets
16 GA wire

I started by creating a new wiring diagram based on the factory diagram converted to negative ground and the one I made for my Hornet. Some of the harness was reused. The handlebar switch, headlight, tail light, and gauge bulb leads to be specific. They were cleaned up and silicone greased to prevent corrosion. I used solder type Lucas bullets and crimp type spades to connect all of the bits and ran a common ground back to a post for most things. I also checked continuity between the engine and frame to make sure it was grounded well.

My first attempt at a diagram with many edits.

Following the diagram to cut wires to length.

Starting to look like a harness.....

Adding connectors.

The final harness....a few things had to be tweaked before it worked.

Lights ready to go after a bit of a stumble with the oil pressure sensor. The toggle was also not working properly and required a blast of cleaner to get it back in order.

The battery box filled with new bits.

The Trispark coil provides a great looking spark & was an upgrade used on my Hornet. A custom bracket was machined from aluminum to hold it in place. The power port is also mounted to its custom aluminum bracket. Lets see how it works. A purist may not want technology but I have found a cell phone a perfect accessory for an antique bike. I like to go places I have never been and this will make me more adventuresome.

My second bike with a Tri-Spark ignition.....a great product in my opinion. Connections soldered to prevent issues. NGK suppression caps and a dual lead 12V Tri-Spark coil round out the system.

Hooking up a battery and testing things out.

I fiddled with the wiring diagram and purchased bits throughout the fall. The Christmas Holiday work break was a great opportunity to tackle this project. (My plan ran afoul when I ran out of connectors and had to move on to my mechanical fixes) Although it will run battery free I hooked one up to test it out. Everything appears to work fine; lights come on, spark is strong (even with no battery), and the brake lights work. The real test will not happen until spring when I get it on the road. If engine "missing" issues persist new Amal Premiers will be fitted. I have heard good things about them and am itching to give them a go if needed.