March 2021

This recently restored BSA Lightning was going to receive a transplant in the form of a Trispark ignition unit along with Trispark coils.

The owner had purchased all the bits, including a new alternator stator, as there seemed to be some charging issues. It all got delivered by trailer so work could begin as soon as I could. Despite a bit of a crowd in the shed, I did so right away.

I seem to be getting a lot of bikes in recently that do not have mainstands, which does make them harder to work on. It also means some form of earthquake preparedness is required. 4" x 2" style...

The bike still had its original points, which are concealed behind the right side cover. Any work here requires this cover to be removed, so kickstart must be removed which can involve a fair bit of persuasion of the cotter pin. It did.

Once the cover was off it was necessary to find some accurate timing marks with which to accurately set the new unit. There was a mark on the alternator rotor, but they can be unreliable, so another was found in the form of a machined slot on the crankshaft, visible through this hole.

This enabled the rotor to be fitted and the Trispark unit to be wired up in place for its first test run.

Because the ignition would now require 6 volt coils rather than 12 volt, the new Trispark coils were also fitted and wired up in their new configuration after removing the airfilters in order to create some working space.

My attention now turned to the other side of the bike. The alternator was under suspicion, so I made some measurements with a multimeter to check whether the stator was viable or not. I could not fault insulation or winding resistance so I moved to the rectifier. That also checked out well, but one of the connections to it was quite loose so I replaced it.

Checking from the rectifier wiring back to the stator now showed some strange readings, so I found the only other connection between the two which was a pair of push-in Lucas jobs beneath the coils. Sure enough, one bullet pulled straight out and was quite black. I cleaned both bullets and fitted a new connector body.

That got us to the first test run. The voltmeter showed we had full charging volts so all was well in the alternator and rectifying dept.

Next step was to check the ignition timing with a strobe light. It was a slight fraction retarded so that was put right. Time to button it all up.

Next thing would be a test ride to make sure all of this behaved as it should under operating conditions. I had two BSA's to test so they were done back to back.

That resulted in two passes, so all that was left was to record the final status of the bike before it left.

The bike was very easy to ride, which always suggests that it is a happy unit. Having not ridden it before the new ignition unit went in I could not appreciate what difference it may have made, but it all behaved well for me, and I felt satisfied that it was complete from my point of view.

The owner collected the bike and elected to ride it home, which pleased me greatly. He even texted me later to say he was quite disappointed when the ride was over, so I took that as a good sign..