ignition failure

Hi all,

Today I finally started my overhauled 912ULS. It runs smoothly, I balanced the carbs mechanically and pneumatically. The latter stuck with trying, because I couldn't get enough RPM (some 3000). Switching off showed no RPM drop on L, and a shut-off when the key turned to R.

So, one ignition box seems to be missing here? I swapped all 4 plugs and tried again: still shut-off when turned to R.

I swapped the key-block for another one, to see if that could help: still shut-off when turned to R.

Now, these items are very expensive, so I'd like to do some investigation before I order a new one: anyone ideas what to do next?