hi my 199B has a nut with a vent tube but i do know there is also a littel vent hole just above the front sprocket. you can buy a nut with a breather just put a tube on it. but if its runing hot it could be a number of things like timming or the carb my not be set up proper. but bare in mind these bikes do get hot if you clutch case or magneto case gets hot then somthing is wrong.