The hoses are open at the end, but air does`nt actually blow out when the engine is running. All the breather pipes do is vent the carbs, to allow fuel to flow into the float chamber. Basically the float chamber is sealed, except for the very small outlets of the jets. The float needle inlet where the fuel enters the carb is bigger than the jet outlets, so if the carbs were not vented, the air in the float chamber would have nowhere to go and the resulting pressure would prevent the bowl from filling with fuel. So air does may exit the tubes, but at such a slow rate you would not be able to tell. If you do try this starting tip, put the choke lever on then blow two or three times into each vent hose.