Something to consider.

http://www.sscycle.com/tech-info/tec...on-oil-filter/

"If you run the 10 micron filter with an evolution style engine it will not be able to return oil through the filter fast enough causing the oil to back up into the lower end robbing power and/or causing oil to puke out of the lower end."

The Sportster oiling system is very basic.
If the ports and pushrod tubes are clear, and gaskets lined up correctly, the only thing left are hoses.