Sprint Filter P08 F1-85 Air Filter for Racing – Kawasaki ZX-25R (2020–2026) PM164S F1-85

Of the eleven machines built around this airbox, the ZX-25R is the one where the flow figure stops being theoretical. A 249 cc four spinning to the kind of engine speeds this one reaches moves an extraordinary volume of air for its capacity, and it does so at the very top of the range where every restriction in the intake path is at its most expensive. The P08 F1-85 flows 15,000 l/m²/sec against the 5,050 of the standard P08 — a margin that most road bikes will never touch, and that this engine, prepared and used as it is meant to be, can genuinely begin to draw on.

Key Features

• Roughly double the filtering surface of other performance filters — area, not just fabric
• Racing fabric: 15,000 l/m²/sec of air flow at a filtration of 85 microns
• A two-year warranty; the element is built to last the life of the motorcycle
• Dry polyester, never oiled; no film to reach four sets of throttle bodies
• Washable and reusable — compressed air from the clean side between sessions
• Replaces the element in the standard airbox — nothing modified, nothing remapped

Where a small four spends its air

Peak demand, not average demand, is what an intake has to satisfy. Four cylinders drawing in quick succession at very high frequency present the element with something close to a continuous load rather than four separate events, and the top of the rev range is where the engine is asking for the largest share of what the intake can deliver. That is precisely the operating point at which a partially loaded filter shows up first, and precisely the reason a race medium is specified for engines of this character rather than for large, lazy ones.

The price on the label, in filtration terms

What the flow costs should be stated rather than skipped. The F1-85 filters to 85 microns where the standard P08 works at 80 — a coarser weave, chosen deliberately. Racing tolerates that because a circuit is comparatively clean, sessions are short and the engine is opened on a schedule measured in running hours. A ZX-25R used on dusty public roads is a different proposition, and there the standard P08 or the P14 at 14 microns is the more sensible choice. The airbox takes any of them without modification.

Care and cleaning

Clean it before the day rather than after it — an engine that works at the top of its range gets least out of an element that went into the van dirty. The service is compressed air from the clean side, directed outwards, and a dry refit, short enough to fit between two sessions. Deeper cleaning is lukewarm water with a mild detergent, a rinse until the water runs clear and a full air dry, with heat and flame excluded at every stage. No oil is ever applied. The Sprint Filter maintenance sheet is in the Downloads tab.

Fitment & Compatibility

Made for the Kawasaki ZX-25R from 2020 to 2026. The same PM164S F1-85 element covers eleven machines sharing this airbox design; the complete list is in the Fitment tab.