Why is it stock and aftermarket HD oil tanks do NOT have threaded oil dipsticks/plug spouts? Is it a pressure thing? My aftermarket horseshoe tank tends to leak oil at the spout. teh stock tank did not. I'll either thread it or invent a seal for it. Any info?

Bug

 

Welcome to the forum, I'm not a hd mechanic but my guess is that it has to do with pressure. Possibly as a safety feature, if you plug it tight you might blow it out somewhere where it might cause damage to the motor. With that said, have you changed anything to do with the breather system?

 

Try a new rubber spacer on the dispstick or a new dipstick altogether. When the rubber on the stick gets dried out it tends to do this.