Does it have an immobiliser? If it's turning over fine then the battery's ok. Even with crappy old fuel in it it should try to run, if you're not getting any life at all then it's electrical - kill switch, side stand switch? Does the fuel pump whistle when you turn on the ignition? Has it got any fuel in it? Mine will often stand untouched for months over Winter and fires up straight away so there's probably one thing stopping it...