Old gas like that can gum up the carbs, if you have the option run a tank or two of 5-10% ethanol gasoline (depending on where you live, “winter gas”, E10, or “ethanol” – just check to make sure it is NOT more than 10% ethanol, as that will do damage to the fuel system – highly corrosive stuff ethanol). It does an amazing job of cleaning out the fuel system.
Also, with it sitting that long, I’d look inside the tank for rust. It may need to be cleaned and resealed (a few hundred dollar job, but waaay better than having it rust through!).
I’ve got to say, I’m a little jealous, I’d happily plunk $650 down on a GPZ305 if one in good shape ever came up around here…
“The two seconds between ‘Oh S**!’ and the crash isn’t a lot of practice time.”