With todays fuel, and the inclusion of Ethanol, one of the worst things you can do to you bike is let it sit for any period of time. Ethanol attacks the rubber in your fuel system, carb, and engine. Ethanol is hydrophilic, meaning that it absorbs and mixes with water. Before you even purchased it from the pump, it was tainted with water, to some degree. If you are not fortunate enough to have a source for purchasing ethanol-free fuel (Pure Gas), then your next best option is a good fuel treatment. Repairs are expensive. Carb cleaning is a pain. Don't go without it!