Sprint Filter P14 Air Filter for Dusty Conditions – Honda CB350 (2021–2026) SM289P14

The two Sprint Filter media offered for this airbox are usually read as the same filter in two grades, one simply tighter than the other. They are not built the same way at all. The standard P08 is a single woven polyester layer that stops particles at a calibrated aperture, rated at 80 microns and 5,050 l/m²/sec. The element in the SM289P14 is a dry special non-woven: not a grid with openings but a mat of fibres laid across one another, so air threads a winding route through the depth of the material instead of a straight one through a hole. That construction is where 14 micron filtration comes from, and it is also why the rated flow falls to 1,800 l/m²/sec. On a plain 350 cc roadster that exchange is easy to defend — but it is an exchange, not a ranking.

Key Features

• A dry special non-woven filtering to 14 microns, never oiled at any stage
• 1,800 l/m²/sec of rated flow where the P08 weave passes 5,050 — the air given up pays for the retention
• Filtering area comes to roughly twice that of other performance elements
• The standard airbox takes it as it is: nothing modified, nothing remapped, homologation unchanged
• Compressed air from the clean side is the routine; washed and used again rather than binned
• Two years of warranty run from the day it is bought

A mat rather than a mesh

A woven layer does its work on its face: a particle either passes an opening or it does not, and once the face is covered the path closes quickly. A non-woven mat catches through its whole thickness, because a particle small enough to enter still has to negotiate fibres behind the ones it slipped past. That gives the medium far more places to hold dirt before the route through it starts to shut, which is what makes a 14 micron rating practical on a road motorcycle rather than merely restrictive.

What a 350 cc single has spare

Flow ratings describe the medium, not the engine. A long-stroke single takes one charge every two turns of the crankshaft, reaches its ceiling early and spends nearly all its life at part throttle. The air it asks for in a second is modest by any measure, and the reserve above that figure is not something a rider ever spends. Handing some of it back in return for a tighter medium therefore costs the CB350 nothing it was using. The honest limit runs the other way round: a finer element collects more and therefore reaches the point of needing attention sooner, and if the bike lives on clean, fast, sealed road the P08 is the better balance.

Care and cleaning

Compressed air does the routine work: clean side, blowing outwards. After a dusty spell a wash is fair: lukewarm water, mild detergent, rinsed until the water runs clear, then open air until it is dry to the core. Keep heat and flame away. Refit it dry; no Sprint Filter medium is oiled, this one included. The maintenance sheet for the SM289P14 is in the Downloads tab.

Fitment & Compatibility

Made for the Honda CB350 from 2021 to 2026. The same SM289P14 element covers five machines built around this 350 cc single; the complete list is in the Fitment tab.