If your carbs aren't balanced well at idle, then one side will be stronger than the other and you will feel that.
I don't know if your bike has points, and I don't know if this applies to the 70-on BMWs, but on the pre-70 bikes with points, the cam that opens the points has two lobes, and they have a tendency to wear differently (especially when they don't get the magic Bosch lube). You end up with differential timing, and it can be significant. One symptom of this is that the bike moves back and forth at idle, and it can't be tuned out.