Recently replaced a head on my 2000 883 sportster. I got it off of ebay and the person said it came off a 99 sportster, the part had a matching casting number on it of 16663-86b. When i went to install the part i noticed that the head breather vent by the carburetor was alot smaller than the 1/2-13 thread breather bolt that was in the old. Head. Does anyone know what the part number on this head is and is the breather vent the only difference. The local Harley dealer looked at me and was puzzled. they said that the thread was the wrong size and had no clue why.