Tappet setting shouldn't be a problem.
I'd imagine though that if the dizzy was 180-deg out, there's be backfiring and popping as you'd be getting a spark possibly with ex/inlet valves open.
Can you stick another carbie on? It's getting the juice but maybe too much. SU carbies wear the butterfly spindle and cause pain but I don't know about Strombergs.
Just thinking...