You have changed your post. To bad.
Your air,oil separator in the tappet cavity is too big. Adding more oil to the crank case only worsens the problem. The motor can't even handle 8 oz of motor oil with the modifications. Adding more Heat, guess what's going to happen.
Running your motor at 30 miles an hour with all the riding that you do, you wouldn't have any problems whatsoever with oil purging. Heat.
Heat from the top of the motor,being transfer to the case, stopping the oil from doing what it's supposed to do.
At what RPM's is there turbulence or from the heat.
I don't have any of these symptoms.
Ray