I've never understood why on twins they put the carb on the bottom between the mufflers. Sure makes it hard to adjust. I read in another thread a guy took the XYZ apart and reversed the heads with some other stuff to put the carb on the top with the mufflers pointing down like a person would want. He said it worked well and not too difficult. However, you needed to make sure the rings didn't interfer with the ports which required flipping something as I remember.