yes thats right,the vaccum tap relys on the vaccum from the carb to open a diaphragm operated valve inside the tap so if theres no vaccum there no fuel.it to prevent the fuel from leaking out if the float needle was stuck of dirty.if its hard to start ot could be many different things, low compression/choke jet or pilot jet blocked.crank seal leaking.reed petal leaking....ect
adam bike doctor
April 2010