Pattern Flyers often use air filters. Most of the air filters I have seen are for larger .91 to 1.60 engines. Central Hobbies carries them. ( http://www.centralhobbies.com/Engines/air_filters.html (You may be be able to adapt a filter from an RC car for a smaller engine. I am trying to find a filter for a .40. I fly off a dry lake bed, and I am concerned about dust.