I'm stealing this from Shortboarder, but I don't think he'll mind:
"ok, just got home + took a look at my bike. *Here's an easy way to tell:
1. take off the rear seat or hump.
2. On the right hand side wall of the compartment, next to the tool bag--if there's a white sticker that has information about fuel vacuum hose routing with a bunch of diagrams, you have a California ("E-33") bike.
3. Also - you can actually see the charcoal canister by looking between the plastic of the storage compartment and the rear cowling on the right hand side. *It's a black cylinder.
If you don't have either of these, your bike is an "E-03" - the designation for non-Cali USA bikes. Pollute at will. "