How many quarts of oil does engine and oil tank hold on a 2000 harley Davidson flht?

About 3 quarts. When you drain the oil & remove the filter, be sure to jack the back of the bike a bit to drain all the oil. When replacing the filter, pre-fill the new filter prior to installing. Then, after you have reinstalled the drain plug and lowered the jack (be sure the bike is on a level surface) add about 2.5 quarts and run the engine until warm. Recheck the oil level per service manual instructions and add oil as needed.