your engine is running lean due to fuel not getting to the carbs, you have to fix this before running or you will be in for a top end rebuild. Check the fuel lines if they are grey replace with black ones from an auto store like will95 said. The gray lines breakdown internally and plug the carb internal filters.
Also take your fuel selector apart and clean it then pull your carbs apart and clean them. If you are carefull with disassembling the carbs you most likely will not need a rebuild kit. There is a small filter in each carb clean it. Should be good to go then.
