You go to the practitioner and buy an air channel there, so about 4x10x60cm of plastic and a flexible air hose with any diameter. Machining: Saw the air channel on the flat side in the middle so about 10 to 15 cm and at the end continue the cut by 90° to the wide side. Then a 15 cm piece is cut off at the other end, and the side wall is removed from it. remain the wide walls. These are cut to a wedge and at the end with the sc hnitt so that a funnel is created and screwed. At the other end the channel is closed, but important: leave a small opening so that the splash water can get out of the back. Then the channel is opened at the side, so that the hose you selected fits in just as well, but does not slip out. This tube is then hung with its other end to the inlet of the air filter and installs the channel so that the funnel in the wind is hung best the radiator grille, or down next to the tire, so that the wind can get in the best way. I did it that way and the “heavy” dirt flies out in the back again, because it, as well as the water through its inertia the 90° corner, where the hose goes to the flutter does not join. Experience worth it!! Have fun crafting!! Do you know what blooms when the bulls of the noticed?