Using one of those analog tachometers that takes a reading off the plug wire never has seemed to work for me. The one I had been using on my Trabant, set to 4 cylinder mode and divide by 2 to get the actually RPM seemed to be bounce around too much.

I'm not sure how you would do it on a Citroen 2CV with a wasted spark ignition.

I bought this one that you point at a pulley off Ebay for US$ 10 with free shipping.

https://www.ebay.com/itm/Digital-Tachom ... 2749.l2649

I placed the reflective tape on the flywheel. Seems to work pretty good. What's good is you can hit the memory button and it will tell you the highest reading.

I tested it on my Citroen and got something weird like 682 RPMs.

That's why it costs only 10 dollars?...
But it's strange indeed..

Actually it seems to be quite accurate.

I got one of these hour meter/ tachometers for a lawnmower. Despite being a wasted spark system, it's giving me about the same reading:

https://drive.google.com/open?id=1X74SO ... Qkt6Lx7G7Y

You wrap a wire around the spark plug lead. Of course this is just "rigged up".

https://drive.google.com/open?id=1Y44KR ... bTGh1IPuqR

I tested the current draw of this particluar coil while I was at it for my Trabant project. About 1/2 an amp.

https://drive.google.com/open?id=1-U6vk ... 59tTVtP_QQ

The primary resistance was around 2.8 ohms but for some reason I could not get any reading testing the secondary resistance.