Welocme Koshin! If the gas is leaking only when the bike is on the side stand then it might be the float bowl seals. Do you know when the PO last messed with the carbs? That's a really cool little bike, have fun with it. It's a far cry from your litre race bike but it's still a blast to ride. Keep us posted, there are some really knowledgeable guys on here. They certainly helped with my rebuild.