Actually, the oil bath filters such as were standard in many of our 'bolts did not depend on the dust being trapped in the mesh. The design is such that the air that comes in (with dust suspended)is headed straight down towards the oil bath and then has to turn back up towards the mesh and then back down towards the carb. The result is that the dust is trapped in the oil bath (before it even reaches the mesh). Actually a very effective design.
