hmm. Are you referring to the notch right on top of the housing/carb? This is just a guideline, when I adjusted my choke at one point the notches were 60* off (my coil was pretty much toast). Does your carb have screws or pop-rivets? All you should need to do to rotate the housing is loosen the 3 screws, if you have rivets then you gotta drill them out.

If you are having trouble putting the housing back on (it can get tricky) think of it like this: the housing is going to contract when it warms up. Hook it up so that this contracting will open the choke plate. Once you're that far, you just rotate the housing (eveythings gotta be cold for this) until its mostly closed (about 1/8th inch open). This way the choke plate will slowly open as the engine warms up.

Dunno if that helps or not, but I'm not quite sure why your housing wont rotate. Try to elaborate on that and then once that moves adjusting is pretty easy.

-Scerb