Modern Vespa

Hi All,

I am in the process of converting my VBB2T from 6 volts to 12 volts electronic ignition, and being a bit of an electrical ignoramus who is colour blind, you can imagine that things are not going smoothly! However, I do have a friend who is a bit of an electrical guru, but he is struggling to help as well; so here is my problem which I do hope someone can help me with.

Bit long winded, so please bear with me!

I have fitted a 12v electronic Bajaj stator plate. Wire colours from stator are: Red, Purple/violet, Grey, Green and Black. Using kickstart, I am getting power from the red and violet (both plugged into cdi), and green. Attaching a wire to the bottom terminal of the CDI, I still get power from the unattached end, but when I attach to coil connecting terminal, there is no power coming through to the HT pin!
If I put my electrical tester pen onto the metal part of the coil, my pen lights! If I connect my cdi to engine case thereby earthing it, no power from cdi to coil!
We have tested both cdi and coil and readings are within tolerances!
I have attached a couple of pics which hopefully may help. I am only trying to get the engine started at this time. Am I doing something stupidly incorrect, missing something obvious?
All help gratefully received. Tia.

The very best move you can make at this point is take the entire Bajaj electronic ignition and remove if from your engine. Once it is removed, chuck it in the trash.

Buy a SIP VAPE ignition.

This was going to be my first statement. I can't +1 this hard enough. That kit is garbage.

Next, you probably want to just replace the wiring harness with a 12v conversion harness. I prefer the BGM conversion harness over the SIP competitor because it comes with newbie-friendly installation instructions and actually connects up to the Vape better than SIP's own offering.

If you decide to try to re-use the old harness, you're going to have a steep learning curve, because the 6v system was what was called "balanced," meaning that it tried to maintain constant load by shorting unused circuits (e.g. the horn and brake light) to ground when not in use.

If that last sentence didn't seem to make sense, just go with the new harness. It'll be MUCH easier in the long run. Just trust me on this one.

Cheers. Going to sell scoot on when it is built, so just wanting to get it running without too much expenditure! I'm aware that the Bajaj system is not the best though, so I will bear your advice in mind!

Thanks. Have already replaced loom with a 12 volt one (Indian). Not got that far yet though, just wanting to get engine fired up!

Is the cdi grounded? Sounds like maybe it isn't.

Sounds like an internal short in either the coil or the CDI.

As others have rightly pointed out, the Bajaj ignition is notoriously unreliable. Endless headaches.

When I attach cdi to engine case, no power from bottom connection of cdi as though charge is going to ground. Unattach, and power is back!

I am not familiar with the Bajaj CDI system; however, since you loose power to the coil when the CDI case is attached to the engine, perhaps the proper way to mount the CDI is via rubber insulators? Worth a try, I'd say.....