The Ciao originally came with a #43 jet. Very late models of the Ciao came with a #49. The Grande carb came stock with a 49, as it had a slightly larger carb, freer flowing airbox, and larger induction chamber in the otherwise identical engine. I also have a #50 in a spare dell'Orto carb, so they go at least that large. FYI, I've tried swapping jets and it requires some fooling around with the airbox also. Just replacing the jet with a larger one doesn't seem to work, as the mix ends up too rich.