Sprint Filter P08 F1-85 Air Filter for Racing – Kove NK321R (2021–2026) PM242S F1-85

Look at the two headline numbers for this medium next to the standard one and they seem to disagree. The racing fabric is rated at 85 microns where the road fabric is rated at 80 — coarser, on paper. Yet in Sprint Filter's own comparison at a 100-micron particle size, the racing sample held back 95.22 per cent against the road fabric's 93.13. Both statements are true, and understanding why is the whole point of choosing between them for an NK321R.

Key Features

• Racing-specification dry polyester, rated at 85 microns
• 15,000 l/m²/sec of material flow, the highest figure in the Sprint Filter motorcycle range
• Measured retention of 95.22 per cent of 100-micron particles in the manufacturer's comparison
• Roughly twice the filtering area of a conventional performance element
• Dry in service, with nothing to apply and nothing to migrate forward
• Reusable for the life of the machine, with a two-year guarantee

A rating and a measurement are different things

The micron rating describes the weave; the retention figure describes what one sample caught at one particle size in one test. Large particles are stopped by nearly any credible medium, which is why the two fabrics sit so close together at 100 microns. The difference between them opens up further down the scale, in the fine fraction, and there the coarser rating means what it says. So the racing medium is not a filter that beats the road medium everywhere — it is a filter that gives away some of the fine end in exchange for a flow figure roughly three times as large. By Sprint Filter's own account this is the sort of medium behind their presence in MotoGP, World Superbike and the support classes, which is a manufacturer's statement rather than an independent measurement, and it describes the environment the part was drawn for: an engine rebuilt on a schedule, breathing air nobody expects to be clean for long.

Whether an NK321R wants it

Most do not, and that is worth saying plainly on the product page. A standard roadster ridden on the road is better matched to the standard fabric, or to the fine 14-micron mat if it lives somewhere dusty. This element earns its place on a machine used for competition, where the intake has been worked on and the extra flow has somewhere to go. On any of them, standard or not, the same limit applies: a filter inside the original airbox does not make a motorcycle noticeably more powerful. It lowers the resistance in front of the engine and keeps that figure stable while the miles accumulate.

Care and cleaning

Blow the PM242S F1-85 out with compressed air from the clean side towards the dirty one, which is all most sessions call for. Water and a mild detergent handle the rest, followed by a proper rinse and unhurried air drying — never a heat gun, never a flame. Refit dry, always. The maintenance sheet is available in the Downloads tab of this page.

Fitment & Compatibility

Fits the Kove NK321R from 2021 to 2026. Two machines share this element, the NK321R and the faired 321RR, both using the same standard airbox; the Fitment tab has the details.