Ok with PJ-1 air filter cleaner (i use their stuff to from riding motorcross) will make these filters new basically. Theres no reason to use a filter and throw it away when you can get it just as clean as when it came out of the package even with a lot of soap and water... you can still get all of the dirt out. Never use stock kyosho filter elements. They are extremly thick forcing the air (and dirt with it) to find its way around the sides of the filter and destroying your motor. Otherwise the stock filter with good element will serv its purpose. Get an oversized element and sandwich it in the mounts to make a tight seal around the sides of the filter and put oil around the sides of the filter aswell. Run a decent dust filter and oil the inside of that too. Check the filter after each tank of fuel and when its looking a bit dirty change the filter and dust filter. When you pull the dust filter over the main filter just make sure you don't pull the main filter out from under the lip in the mounts.