I think if you put fuel stabilizer in the gas tank and run the engine for a few minutes in order to get the stabilizer through the carb you'll be fine.  With outside storage it's a bit more difficult, but I would pick a nice sunny day every couple of weeks and start the engine.  Run it for 15 or 20 minutes so it gets good and warm.  My last bike had a center stand and I would even put it in gear and let the transmission and drive mechanism work for a while.  If you're talking about long-term storage, maybe a year or two, or if you can't run it frequently that's a different matter.

JR