Sprint Filter P08 Air Filter for Road & Track – Royal Enfield Hunter 350 / Hntr 350 (2022–2026) CM231S

An air filter can only be cleaned if what it stopped is somewhere an air line can reach, and that is not a given. Pressed paper and non-woven mats catch particles inside their depth, held in a tangle of fibres — excellent filtration, and a poor basis for reuse, because what goes in stays in. A woven cloth works at a face instead: the threads form an even mesh, the load builds against the outside of it, and air can push it back off the way it came. Everything the Sprint Filter CM231S offers a Hunter 350 follows from that one structural difference.

Key Features

• Single-layer polyester weave, dry, filtering at 80 µm with a rated flow of 5,050 l/m²/sec
• The load collects on the face of the cloth, where compressed air can lift it away again
• Thread diameter from ø 22 microns; the openings between the threads set the filtration figure
• No oil at any point, so nothing tacky is held in the mesh and nothing travels downstream
• Drops into the standard airbox in place of the factory panel — no modification, no remap
• Kept for the life of the motorcycle rather than replaced; two years of warranty from purchase

Why the air goes the other way

The instruction to blow from the clean side outwards is not a formality. The dust arrived travelling inwards and came to rest against the outer face of the weave; air sent the same way would press it into the mesh and finish the job it started. Sent backwards, it lifts the deposit off the surface it is lying on and puts it back outside. That is why the element returning to the Hunter is close to the one that came out of it, and why a filter here can be a fixture rather than a consumable.

The other kind of element, honestly

Depth filtration is not a mistake. It is exactly what you want when the air is genuinely dirty, and Sprint Filter builds for that too: the P14 non-woven listed for this airbox holds down to 14 µm and flows 1,800 l/m²/sec. It catches far finer particles than an 80 µm weave, and gives up flow to do it — a trade, not a ladder to climb. What no element of any kind does is add power: a drop-in filter cannot make a standard 350 single noticeably stronger, and the comparison worth making is between a part that gets serviced and one that gets bought again.

Care and cleaning

An air line on the clean face, worked outwards, covers ordinary service for the CM231S. Where the deposit is oily instead of dusty — a crankcase breather leaves a film that air will not shift — lukewarm water with a mild washing-up liquid and a clear rinse deals with it. The element then dries in air, in its own time, and never with a hairdryer, a radiator or a flame. Refit it dry and untreated; the maintenance sheet is in the Downloads tab.

Fitment & Compatibility

Made for the airbox of the Royal Enfield Hunter 350, also written Hntr 350, built from 2022 to 2026. Four further machines share the element: the Bullet 350 from 2023, the Classic 350 from 2022, the Goan Classic 350 from 2025 and the Meteor 350 from 2021. The Fitment tab carries the full list.