It connects the fluctuating crankcase pressure to the carb so it can pump gas. In your case, it's a short tube (3 inches) that connects to the bottom right of the carb and then to the crank case. Look in between the tank and the crankcase just below the boot. Unless you want to take the tank off, use a pair of curved medical forceps to remove and replace it. You will need to remove the carb and the throttle linkage first - remove the black cap on the handle to remove the linkage.