Test the PCV system.
Pull the fresh air line from the valve cover. Put your thumb over the hole. Over about 10 seconds, the crankcase should pull enough vacuum to suck your thumb to the hole.
If this does not happen you will have to verify that there is vacuum to the PCV valve, that the oil seperator is not plugged, and that there are no air leaks into the crankcase.
Even if oil were building up on the head, a properly operating PCV system should keep it from going back up the fresh air tube into the intake tract. You can always check by looking in the oil fill hole after it's been running awhile.
If the PCV system is evacuating the crankcase, you may have to remove and check the oil seperator or check for excessive blowby.
