There is a cover over the carb on this model. I did not want to force the red knob off the choke adjustment. Seems it was on their pretty good. Looks like the carb nut is a star head screw. There are some holes in the side of this cover, but they don't seem to line up with the carb screw. Any suggestions for getting the coke knob off or getting to the carb screw most welcome. Thanks. Brian