What vacuum lines the bike has depends on the year of manufacture and what smog stuff it has on it. Your can take some WD40 and spray the carb holders, vacuum lines and such places where and vacuum leak might exist with the engine running and perhaps find it. However, this sounds more like a fuel level or debris in the bottom of the bowl problem than vacuum. A diagram of the vacuum lines will be in a good quality Service Manual such as Clymer's or Haynes. You should get one for your bike. They have a lot of valuable information in them.