I experienced one of the last 'iron' 350 Bullets doing exactly as you describe and in this instance it had blown the composite head gasket, internally by a very small amount between the cylinder spigot and the right rear barrel / head stud hole. Some compression was escaping down the stud hole and blowing into the crankcase, nothing was blowing out into the outside world. In this case, I noticed a loss of power and saw the oil dripping from the right tool box while at a junction, close to home. You might get lucky and fix it by tightening the head nuts, or you may need a new head gasket to fix it. B.W.
Any help would be appreciated. Yesterday went for a ride and I got about 30 miles into it when I noticed oil pouring out of the air filter box. There were no other issues with the bike. I know that the breather tube vents to the air filter, and ALL the oil was pushed out through the breather tube. Luckily I noticed it at a stop sign, shut down the bike and trailered it home. So I'm pretty sure there's no damage due to oil starvation. Now I'm just guessing here but it seems that either the oil pump failed or the oil return line is clogged. Are there any other possibilities? Also, how do I go about troubleshooting this problem? Is there an easy way to determine which it could be. I'm not a mechanic, but I have the next best thing... a friend who is fairly competent with bikes.
I would say your analysis is off target. I think the last post by Spitting Bull is very valid along with Ace's suggestion. The only thing to add is to check the drain hose to the timing cover which is likely clogged, allowing the can to overfill. I think it was Pete Snidal that suggested putting an inline petcock on that drain line and plugging the nipple off of the timing case. If you do something like Pete suggests you would have to open the petcock on schedule so you don't overfill the can. A complete removal of the system and rerouting the duckbill from the catch can to the rear of the bike is the best fix that has been done by many members.
It may well turn out that I am 'off target' in this case, but I thought it worth mentioning my experience, as the symptoms are the same and a new head gasket fixed the machine I refer to. As has been said, 'Any help would be appreciated'. B.W.