Yes. you can only rotate it 180. not 90 or 270 (1/4 or 3/4 turns).

I may not be using the proper terms for the parts im talking about, but the colored outlines on the pic will be sufficient for you to understand what im talkin about. The pic Iattached is from when I totally tore down my engine and carb to clean and inspect it after a crash. So, you dont need to take apart the carb at all like I have pictured.

There are two screws that go all the way through (im going off memory because Im on duty so I hope it's pretty accurate) the carb, through the reed valve and the reed valve "case" or "housing", and into the crank case "back plate" (back plate is shown in the first picture, outlined in red) where the air/fuel mixture enter the engine. The carb and reed valve/housing (shown in the first pic, outlined in green) will be together (lets call that the carb assembly), just leave the screws in it and dont even separate the carb assembly.

Simply remove those screws along with the carb assembly as one unit, from the back plate and flip it upside down. Screw it back in and you're done...

Now I know you wont do this, but Icould see someone removing the 4 screws of the crank case back plate and trying to rotate that, and leave the carb bolted on to it. You could do this and think its fine if the piston is up, but it wont work because the piston skirt will come down and slap it. If you had it off you could look at the side that goes into the crank case and see there is an angle for clearance of the piston skirt. This is shown in the second picture outlined in blue. The angle might also be there to let the air/fuel mixture pass through to the intake port. Either way, dont rotate it. Its there for a reason.

Jeremy