Modern Vespa

I have just finished converting my 180 Rally to electronic ignition. In the process it was also converted to 12V.

I used a P200 flywheel from which I removed the center piece. I then had it machined so that the existing flywheel rotor (on the 180) fitted perfectly.

I also used a P200 stator, but had do some machining and filing at the backside to make it fit on the engine. To get the correct timing (22°), I also had to lengthen the screw slots on the statorplate.

It now runs like a dream, but I have been wondering: does the electromagnetic field generated by the rotating flywheel have an influence on the timing light? Why I ask is because the timing was about 15° out when I checked it, hence the machining of the screw slots.

For those who have been wondering: I marked the position of the keyway on the P200 flywheel before I removed the center piece, and I made sure that the rotor's keyway aligned perfectly after assembly. So, why was the timing still so much out?

Itd make sense if all the woodruff key slots were machined to the same spot in the rotation, but I'm guessing they had to mix and match the woodruff key slots to have the crank balanced. More metal here means we have to cut there?

I've seen the same thing if you add an electronic ignition to a P125 points motor. Timing was way off with the 125 flywheel. Put a P200 flywheel on and timing was perfect. Or, I could have machined the slots. Crazy Italians

Come to think of it, I had the same experience when tried to convert my P150 to electronic ignition. I thought something was drastically wrong, so I changed it back to points ignition.

A question: how do you know when a CDI unit is not performing as it should? Does it work perfect one day, and then dies suddenly, or does it fades with time?

I've seen CDIs fail outright (easy to solve) and then fail mid ride.

First case I would have no spark at home, easy swap and go.

Second case which was harder to figure out I'd stop for a drink and then it wouldn't spark. Dick with it to the amusement of the bar patrons and then give up and trailer home. The next day it'd magically work. It was like the CDI internals needed to cool down/discharge and then it would work fine until the next time I rode and stopped and nothing. Few cycles of that and I caught on.