Sprint Filter P08 F1-85 Air Filter for Racing – BMW R 1250 R (2019–2023) K142S F1-85

Two different things fill and empty this element's specification. What the cloth can pass at its limit is a throttle property: it appears only when the engine is asking for everything, which on a naked boxer means a second here and there. What the cloth collects is a volume property: it accumulates with every litre of air the engine has ever drawn, at any throttle position, in traffic as much as anywhere. The catalogue's hundred per cent more filtering surface acts entirely on the second one.

Key Features

• Dry woven polyester at 85 µm, the most open medium Sprint Filter offers
• Twice the filtering surface of the standard-size racing element for this airbox
• The highest rated flow in the range, 15,000 l/m²/sec of material
• 95.22 per cent retention of 100-micron test particles in the manufacturer's comparison
• Never oiled, at any point, so the throttle bodies and sensors stay clear of any film
• Blown clean and refitted for the life of the machine; two years of warranty

Loaded by volume, not by effort

An engine idling through a city draws air continuously, and all of it crosses the filter. Over a year the total volume moved by a machine used for short journeys in traffic is not far off the total moved by one used for long fast ones — what differs is how it is distributed in time. Since the load an element carries is set by that volume and by what the air happened to contain, a roadster ridden every day accumulates at a decent rate while almost never approaching the flow figure on the box. Twice the cloth is twice the room for that.

And the figure that stays on the box

The 15,000 l/m²/sec belongs to the other kind of use. It was drawn for wide throttle held high in the range and returned to repeatedly, which is a circuit description, and an unfaired machine reaches that state briefly if at all. The standard weave for the same housing is rated at 5,050 l/m²/sec and has never yet been the thing in the way. The sensible summary is that the medium is optional on an R 1250 R while the area works every day. Neither is a power part: an element inside an unmodified airbox leaves a standard R 1250 R exactly as strong as it was.

Care and cleaning

An air line and a few minutes cover it. Point the nozzle at the face turned towards the engine so the load is pushed back out of the weave rather than through it, and keep the pressure sensible. If a film has settled that will not blow off, wash the cloth in hand-warm water with a trace of mild detergent and rinse until nothing more leaves it. Then let it dry in moving air, completely and at its own speed, keeping every source of heat and every flame well away — that, rather than dirt, is what finishes a polyester element. The K142S F1-85 goes back dry. Downloads holds the servicing sheet.

Fitment & Compatibility

Made for the BMW R 1250 R of 2019 to 2023, seated in the standard airbox with nothing modified. Six catalogue entries sit against this part number, covering five machines: the RS and RT of the 1200 generation and the three 1250 road boxers. The Fitment tab lists the years for each.