I put a vent line inside fuselage for the metering diaphragm covers on all my gas engines. It takes about $.25 and fifteen minutes (after you've done one). Go you your local hardware store and pickup the brass fitting in the plumbing aisle, solder it to the to the cover, drill a hole through the cover, and put silicone over the existing hole. The brass fitting is used on the small polyline that is used with ice makers and furnace type humidifiers.

Chuck