We drag race and hill climb in the sand (dumont, sand mountain) we use a K&N with an outter wear. That being said the K&N works great if you use it in course sand but in fine powder type of dirt the K&N filter will allow fine dirt to pass through the filter and get in the engine. If you oil the filter too much then it stops the flow. Our drag bike is a banchee 725 on a lone star frame with 160 hp to the rear wheel runs on alky and we service the filter every day. Just my opion and observation