If Strombergs are the same as SU's with regard to the choke, the choke adjustment gives a small rise in rpm before it starts to enrichen the mixture. Approx first 1/8" of the choke when you pull it out gives this initial increase. This is very useful during warm up as it will often stall if you put the choke all the way back in. This small amount gives enough revs to keep it going without the slight lumpiness you can get when it's too rich. Check the manual for how to set it up.