[JohnW]

At the end of the day, you need a filter on the carb intake. Yes, the A Model did not come with a filter. However, if you plan to keep the inside of your engine clean you will need one. Just because you cannot see the dust does not mean grit is not entering through the carburetor. Modern filters remove dust particles that are measured in microns. Many people install a maze and then never change the filter. These filters should be changed at least once a year. They should be changed even more frequently if you drive a lot.