Update:
After first start-up, the engine was running with quite a ticking noise at the top-end. I guessed it was a exhaust leak right at the gasket at the engine, and after tightening it (I am too careful not to pull threads out), it finally runs quite smooth. Obviously, carbs need adjustment from here on.
I made a couple first test rides, but found I have no battery charging.
I'm thinking my reg-rec combo is not working properly, as I am not getting any 12V at the white wire which should activate the field coil, and therefore the generator.
I also ordered a new silencer.
Have to say, the bike feels real nice going around town.