Motocross air filter

Buying a motocross air filter: The key choices

Avoid costly repairs and keep the following in mind when ordering a new filter:

• The perfect fit: A filter that leaks will let sand through. Every airbox is unique. Always use the MXProStoreParts Partsfinder to match the filter to your bike's brand and model year.
• Pre-oiled or dry: Want to hit the track right away? Choose a 'pre-oiled air filter'. These are already perfectly and evenly coated in oil at the factory.
• 4-stroke (Fire Resistant): Riding a 4-stroke without a spark arrester in the airbox? Always install a fire-resistant air filter. A backfire from the throttle body will ignite a standard filter immediately.
• Dust covers (GP Cover): Riding in bone-dry sand? Fit a dust cover (filterskin) over your filter. Pull it off between motos and you’ll have a clean, fresh filter again.

Step-by-step guide: Washing and oiling your air filter

Once the tracks dry out in spring, the air filter is the most ordered replacement part in our workshop. You should replace (or clean) your air filter after every dusty ride. Our Pitcrew team has these key rules for all foam filters in our range:

Step 1: Use the correct materials (No gasoline!)
Washing your filter? Never use gasoline or turpentine. These products will dissolve the industrial adhesive that holds the foam layers together. Submerge the dirty filter in a bucket of specialized cleaner (such as Twin Air Dirt Remover). Use a bucket with a bottom grate so you don’t wash the filter in its own dirt. Gently squeeze out the dirt. Never wring the filter out — the twisting forces will tear the foam straight apart.

Step 2: Rinse thoroughly and let dry completely
Rinse the filter thoroughly in a bucket of warm water and dish soap. Keep rinsing until the water stays completely clear, so you know all leftover dirt and old oil has been removed. Let the filter dry for a minimum of 24 hours. If the foam is still damp, the new air filter oil will not adhere and unprotected gaps will form.

Step 3: Oil correctly
A dry filter will not block sand. The extremely sticky air filter oil is your actual trapping medium. Submerge the filter in the oil and work it in thoroughly for even distribution.

Pitcrew tip: Put the oiled filter in a clean plastic bag to work the oil in — this will save you from getting very dirty hands. Squeeze out the excess residue until it no longer drips. Let the oil evaporate for a minimum of one day. The thinners must evaporate, otherwise your engine will temporarily run too rich.

Step 4: Pro tip – The sealing rim
Air always takes the path of least resistance. Always apply a generous layer of Twin Air Bio Sealant (or similar filter grease) to the sealing rim that presses against the plastic airbox. This creates a waterproof, durable barrier. Do not use regular assembly grease on the rim — it will melt away from the heat of your engine block.