Vespa Air Filter
Air filters work simply to make sure that the air entering the combustion chamber is clean. These filters are the metal wire gauze type and they really never wear out. Every 3000 miles or so the air filter should be removed and cleaned by soaking in new gasoline to remove any accumulated dirt.
Large frame Vespas typically have the air filter either in the carb box mounted on the engine or, in older models it is mounted directly to the carb under the seat. Small frame Vespas have an air filter mounted to the carb which is accessed by removing the plastic glove box under the seat. It is removed by small wing nuts on the front side and can be cleaned by washing in clean gasoline. Access is through the under seat door.
Above are two filters which mount inside the carb box. Over the years the filters have changed so if you do have to change the filter, make sure you find the correct replacement. Above is a P200E (VSX1T) and a Vespa 150 (VBA1T) filter.
Basically the air filter is a wire mesh which is either directly connected to the carburetor or housed in the air box. To gain access to the filter it is necessary to remove the right hand side engine cowl. Locate the air box which is at the end of a flexible rubber intake tube. Your model may vary but apart from small frames the set up below should look familiar.
Remove the two philips head screws (arrowed) and remove the top of the air box. Be sure to leave the rubber sealing strip around the join in place, as well as the other assorted rubber grommets.
The air filter on a P-series bike is held directly to the carb by two flat head slotted screws. Remove the filter and wash it in clean gasoline to remove any residue. Air filters don't really wear out as long as they are kept clean there should be no need for replacement.