Sprint Filter P08 F1-85 Air Filter for Racing – Honda CB400F (2019–2026) CM220S F1-85

Almost every filter is sold as an improvement in both directions at once. The P08 F1-85 is unusual because it openly moves in two directions: it flows 15,000 l/m²/sec against the 5,050 of the standard P08, and it filters to 85 microns instead of 80. That second number is a step backwards, and it is deliberate. Racing accepts coarser filtration because a race engine is opened on a schedule measured in hours, not in years — the wear that a slightly coarser weave allows is wear that gets inspected long before it matters. On a Honda CB400F that is only a sensible bargain if the bike is maintained that way. The CM220S F1-85 is a competition part, and it should be bought as one.

Key Features

• At 15,000 l/m²/sec the P08 F1-85 medium passes roughly three times what the standard P08 does
• Filtration at 85 microns: a coarser weave than the road medium, and deliberately so
• Polyester, dry, never oiled — nothing that could migrate onto a sensor or a throttle body
• Around twice the filtering area of other performance elements
• Installs in the standard airbox with no modification and no remap
• Reusable; compressed air from the clean side is the whole of the service

Filtration is what you are spending

Sprint Filter's own comparison figures put the standard P08 at 93.13 percent retention of 100 micron particles and the F1-85 at 95.22 percent — but the media are measured at their own apertures, and the F1-85's is the wider one. In a race context that is a rational trade: the air on a swept circuit is comparatively clean, the sessions are short, and the engine is stripped often enough that nothing accumulates unseen. On a road-ridden CB400F covering thousands of kilometres between services, the same trade is being made without any of the maintenance that justifies it.

What it will and will not change

Fitting the CM220S F1-85 does not add power to a standard 399 cc twin. A stock engine is not limited by its air filter, and the extra flow sits unused behind a standard airbox, standard throttle bodies and standard mapping. The medium starts to matter at the end of a chain — when intake, exhaust and mapping have already been opened up and the engine is genuinely asking for everything the intake can deliver. Bought for a standard road bike, this element is an expensive way to filter slightly less well. Bought for a machine that races, it is the right part.

Care and cleaning

Oil never touches it and heat never dries it — those two are constant. The cleaning itself is a compressor: air from the clean side, worked outwards, and the CM220S F1-85 refitted dry. Where a weekend has left more than air will lift, lukewarm water with a mild detergent does it, rinsed until the water runs clear and then dried right through in the open, well away from any flame. The Sprint Filter maintenance sheet is in the Downloads tab.

Fitment & Compatibility

Made for the Honda CB400F from 2019 to 2026. The same CM220S F1-85 element covers six machines across the 400 and 500 twin range; the complete list is in the Fitment tab.