The air filter is a critical component of your engine. We cannot stress enough that for proper care of your engine, the air filter must be in proper working order. 

The air filter in all of our Nitro models must be cleaned and re-oiled on a regular basis. To clean the air filter, take the foam filter element out of the rubber boot and use fresh Nitro fuel to rinse the dirt from the foam element. Use your fingers to work the dirt out of the foam. When all the dirt particles are removed (this may take several rinses), squeeze out any Nitro fuel and allow to dry naturally.

Then apply a small amount of foam element air filter oil, which you can purchase from a motorcycle or automotive shop, or specific r/c air filter oil from your local model shop.

The filter should feel 'tacky' to touch and not 'soaking wet' with oil.

Install the foam element in the rubber air filter boot, making sure that the foam is fully seated in the boot with no open spaces around it that air can leak through.