Let It Breathe: Maintaining Foam Air Filters

Dirt-bike season is upon us again and if you’re wanting to kick up some dust, you should make sure your machine can breathe. Cleaning a foam motorcycle air filter is a fairly simple but important process that is essential to engine longevity.  For those in Australia this can be quite crucial as we’re frequently riding on dry, dusty roads.  Even in Winter!  

Personally, I will check my air filter after each ride (the filter pictured here has 4 hours of use).  This is because I ride with anywhere from two to a dozen other bikes and, most often, I am in the thick of a dust plum which is being sucked directly into my airbox.  A quick look inside the airbox will provide an indicator of the general condition of your filter.  If the box is clean and there are no, or minimal, particles on the filter, leave it be, close the box and go for a ride.  If, on the other hand, it looks a bit grubby, you really need to clean the filter.  

Firstly, remove all loose items that were sucked into your air box: leaves, sticks, small birds, children etc.  Once you’re able to remove the filter without any debris falling into the air intake, remove the foam filter element.  Most modern filters will sit on a small trellis to provide support against the velocity of the engine induction.  The trellis should come out with the foam element and will need to be separated from the element.  Be sure to clean this too.  

With the foam filter element out of the bike, shake or brush off as much rubbish as you can but don’t use compressed air.  With the residual muck gone, you’re ready to begin cleaning the filter.   

For many decades, in fact all of my decades on planet Earth, I used to wash my oil filters in petrol and then squelch some engine oil into the foam, job done.  Anyone even remotely familiar with motorcycle maintenance reading this would recognise the folly of my actions.  By using a solvent, I was degrading the foam element and lathering it in engine oil was making it harder for the engine to breathe.  Instead of going to the shed for a cleaning solution, I should have been going to the kitchen.    

Think back to high-school science and recall how simple, house-hold detergent will break down grease by helping oil and water to mix. This will work for your foam air filter element and enable the gunk to be washed away. There’s no need to use petrol.   

Drop some oil-filter detergent into a bucket, then simply wash the element as if you’re doing your best cashmere jumper. We recommend Motorex Air Filter Cleaner which is biodegradable and free of solvents that will degrade the air filter element.   Once it’s clean, squeeze the excess water out and allow the element to completely dry.   

Once the filter is dry, apply a liberal coat of air filter oil.  Again, we recommend Motorex Air Filter Oil.  An added advantage to the Motorex product is its rich green colour.  Being coloured, you can easily apply the oil evenly over the entire element.  This is a departure from my previous efforts at using engine oil insofar as the Motorex product is much thinner than engine oil and it will allow air to more easily pass through the foam, with the oil trapping dirt and dust particles.  

Truth be known, when I’m unleashing 60 horsepower on a dirt road, the last thing I am going to notice is the difference in air filter oil viscosity but when it comes time to clean the air filter again next week, washing the element will be much easier.