Air Filter Element Two Slots Feed Two Intakes

This air filter is not round; it is split into two slots in the middle, because the machine has two intakes. The CRM250 air filter element is exactly that twin-slot build.

Why two slots? The carburetor side of the machine has two intakes, one throttle bore each, and both need air at once. The slots in the middle of the element sit on the two intakes, air passing through the slots, neither one starved and neither one fighting the other. A round element cannot cover two intakes, and where it covers, it leaks, so the slots are cut to the shape of the intakes, two intakes, two slots.

What does each foam layer do? The green outer layer is oiled coarse foam, the oil film trapping the big grit and debris, the first sieve. The white inner layer has finer cells, taking the fine dust that rides in with the air. One coarse, one fine, the engine breathes clean, and the green layer still breathes, so both throttle bores get their air without strain.

What is the black rubber ring in the center for? The ring lines up with the machine's intake passage, hugging the edge of it, air passing through the ring and not leaking around it. The ring is soft and seals under pressure, but it does not like dirt, so wipe the passage mouth before fitting and keep the ring from wrinkling.

Why is it oval? The element seats into the air cleaner box, and the box is oval, so the element is oval, the edges closing all the way around, the air taking only the two paths of the slots and the ring, not sneaking out through the seams.

Can it be washed? Yes. Take it off and wash it with a dedicated cleaner or clean water, never gasoline, which eats the oil film. Squeeze it gently, let it dry, thin it with a coat of air filter oil, and refit it. Once it hardens, crumbles, will not wash clean or tears, swap it; foam ages, and a clean wash does not make it last forever.

What to check when fitting it? Line up the position of the two slots, the position of the center ring, and the oval curve on the new element against the old one. Machines of the same type mostly fit, but fit is not guaranteed for every one, so comparing against the old part is the safe way. Press it flat into the box, slots on the intakes, ring on the passage, snap the box lid on, and only start once the air path is tight.