Its not really a big deal if a few tiny dust particles get into the engine, it won't ruin anything. In fact i ran several laps the other day when my filter fell off and i didn't even notice it. No damage was done to the engine. In fact airplanes and boats don't use an air filter at all. Its just the larger pieces of dirt that you don't want to get into the engine. That will scratch up the piston and sleeve and could ruin the engine very easily.