How much motor oil does a Harley Sportster hold?

It would be best to read the owner's manual to learn what the factory recommends. However, most Sportsters (depending on specific model) hold roughly 3 quarts of oil. It is recommended enough oil be added to the filter to soak the filter media, but not run out while it is being installed. Then, add enough oil to the engine to bring the level to the mid-way point on the dipstick.