Sprint Filter P08 F1-85 Air Filter for Racing – Honda H’ness CB350 (2020–2026) SM289S F1-85

A good many intake parts are bought for how the bike will feel and sound afterwards rather than for anything that could be measured, and the H'ness CB350 — a machine whose exhaust note is half its appeal — attracts exactly that kind of shopping. It is fair to say plainly what the SM289S F1-85 changes and what it does not. It raises air flow from the standard P08's 5,050 l/m²/sec to 15,000, and it lowers filtration from 80 microns to 85. It does not alter the induction note, because the airbox, its intake snorkel and its lid are all left exactly as Honda made them. Nothing about this part is audible.

Key Features

• Sits in the standard airbox unchanged: no modification, no remap, nothing to notice
• Its rated flow is 15,000 l/m²/sec, roughly three times the standard P08’s
• The retention given up for that is the step from 80 microns to 85
• Dry polyester, never oiled, so no film can reach the throttle body or the sensors
• Filtering surface about double that of other performance elements
• Every service ends with the same element refitted, cleaned rather than bought again

What people are usually buying, and what this is

The wish behind most intake purchases is a sharper response and a deeper intake growl. Both of those come from the housing, not the element: the volume of the box, the length and diameter of the snorkel, and the seal of the lid. A filter can only ever give back the restriction it caused itself, and a clean element on a standard 350 single was not causing much. If the noise is the point, the honest answer is that the part which would deliver it is the airbox, and opening one up on a registered road bike brings consequences — noise approval, weather protection, water separation and fuelling — that go far beyond a filter element.

The number that moves the wrong way

The 85 micron aperture is coarser than the 80 microns of the road medium, and coarser means more of what the air is carrying reaches the cylinder. Racing lives with it because a race engine is dismantled on a schedule counted in hours and anything that got in is found before it matters. A H'ness CB350 is not that engine. If this element appeals for its build quality and its washable dry construction, the standard P08 has every one of those properties at 80 microns and 5,050 l/m²/sec; where the air is heavy with dust, the P14 goes further again at 14 microns and 1,800 l/m²/sec.

Care and cleaning

Everything about the routine is dry. Dust comes out with compressed air aimed at the clean side and blown outwards; road film comes out with lukewarm water and a mild detergent, rinsed until the water runs clear. What follows a wash is time in open air — heat or a flame would deform the medium, so neither is used. The SM289S F1-85 returns to the airbox dry, and no oil is applied before, during or after. The maintenance sheet is in the Downloads tab.

Fitment & Compatibility

Made for the Honda H'ness CB350 from 2020 to 2026. The same SM289S F1-85 element covers five machines built around this 350 cc single; the complete list is in the Fitment tab.