The K&N R-0990 is a universal clamp-on engine air filter for the 1968 Norton 750 and 850 Commando. It uses an oval, dual-flange cotton gauze element with molded rubber flanges that seat on the intake without a custom housing. Because the media is washable and reusable, you clean and re-oil it at service intervals instead of buying a new disposable paper filter each time, and the manufacturer rates the filter at up to 99% efficiency. Its high-flow design is also aimed at improving throttle response and engine performance over a stock filter.
The rubber flanges absorb vibration and can be stretched about 1/16 inch (1.5 mm) to bridge in-between intake sizes, which helps if your stock boot is worn or the diameters are slightly off. Check the flange dimensions against your carburetor or intake before ordering, since the filter is universal rather than a direct-fit part. Search terms this filter matches include 1968 Norton Commando 750 air filter, Norton 850 Commando clamp-on filter, washable oval rubber intake filter, and K&N R-0990 cotton gauze replacement. Expect to revisit carburetor jetting after the swap, as the seller data suggests airflow changes can require adjustment.
Yes. The manufacturer states that K&N universal air filters are washable and reusable, and it specifies a re-oiling amount of 0.57 oz (17 ml) for this filter.
The manufacturer says the molded rubber flanges can be stretched up to 1/16 inch (1.5 mm) to fit in-between sizes, though you should still confirm the flange diameters against your intake before ordering.
