I think it would be advantageous to ask some of the riders who put lots and lots of miles on their bikes and see what they have or haven't done. (Maybe you've done that already?). I don't know all of them but I could name a few if you need.

Well, with all respect, I've spent years so far doing nothing but reading XLF threads of what others have done.
It's disheartening to read 'this is what I've done and this is what you must do" when there hasn't been much actual testing other than the fact "it worked for me".
That is not evidence that it'll work for the next guy with all the different engine configurations out there.

I've been working my ass off trying to learn as much as I can.
But I don't have high lift cams and damn the torpedo compression.
Neither does a lot of folks who "must do this".

See my point?

It is a fact of physics, that smaller bubbles, if small enough, will take a lot more time to come out of solution (they float to the top very much slower). If a given scenario is making tiny bubbles then you could have foamy oil or some kind of compounding problem.

One thing that would make bubbles smaller, is higher pressure. As the pressure is relieved, the bubbles would grow again and come out easier.

Any bubbles would also affect the perceived oil level.

There are actually formulas to figure out what size bubble does what in a given fluid. Thats getting way way way in the weeds though. My gut tells me that we're not dealing with significant pressure changes enough to make a measurable difference. But, I'm just throwing it out there.

Yeah my schooling didn't go that far.
But I do know that air and oil don't mix.
It's the churning when there is too much oil in the sump that allows more oil to ring around the wheels and cause froth in the tank.

edit:
But when this happens, it drastically drops the RPM of the engine.
If you're pump isn't keeping up, you're not going as fast either.

I also contend that blowby or added air on upstroke will yield a higher dense air/oil mix, as in the case of my RPM drop with the oil cap off.
When suspended oil gets thrown back to the sump faster than the oil pump is receiving more oil from downstroke. is when the tiny bubbles get into the scavenge port.

My contention is a lower pressure in the sump area allows this to happen.
If there is more positive in the sump, the suspended oil thrown down has a longer road to the scavenge port and more time to separate or get picked back up.
We speak of this in terms of a positive slow start and stop of the pistons but everything is happening quite quickly in the crankcase.

Credits for this article
 

I've left the credits out for a reason.
I didn't want to name drop but rather discuss the issues without he said / she saids, which does taint a good discussion.

But now I realize it appears that the information was made up in my head.
The origins of this thread are a culmination of many members here that do have a lot more schooling and experience than me.

Four Speed, you bring up some good questions but seem to back off conversation with me.
That's fine, I just want to clear up that I'm both following other's lead as well as concluding on my own.
Information given to someone is useless without them receiving it.

So here is a list of all the folks who have their thoughts and endeavors represented in this thread.

1)
Deimus of the XLFORUM http://xlforum.net/forums/showthread.php?t=73243&page=4

2) , 3) , 4) , 7) , 99)
Dr Dick of the XLFORUM http://xlforum.net/forums/showthread.php?t=1204854

5)
cjburr of the XLFORUM http://xlforum.net/forums/showthread.php?t=73243&page=3

6) , 23)
aswracing of the XLFORUM http://xlforum.net/forums/showthread...=59421&page=27

8) , 14) , 15) , 16) , 17) , 18) , 19) , 20) , 28) , 29) , 40) , 41) , 42) , 43) , 84) , 110)
drawing by Hippysmack

9) , 30) , 63)
photo by Hippysmack

10)
Dr Dick of the XLFORUM http://xlforum.net/forums/showthread...1204854&page=4

11)
Dr Dick of the XLFORUM http://xlforum.net/forums/showthread...1204854&page=3

12)
https://www.setra.com/blog/vacuum-pr...you-measure-it

13)
https://www.dekkervacuum.com/resourc...hat-is-vacuum/

21) , 22)
maru of the XLFORUM http://xlforum.net/forums/showthread...d+valve&page=8

24)
Jorgen of the XLFORUM http://xlforum.net/forums/showthread...d+valve&page=9

25)
aswracing oftheXLFORUM http://xlforum.net/forums/showthread...1946516&page=4

26) , 50) , 54)
bunny32 of the XLFORUM http://xlforum.net/forums/showthread.php?t=67658&page=2

27)
bunny32 of the XLFORUM http://xlforum.net/forums/showthread.php?t=67658&page=6

31) , 74) , 96)
aswracing of the XLFORUM http://xlforum.net/forums/showthread...d+valve&page=6

32)
thecarfarmer of the XLFORUM http://xlforum.net/forums/showthread...1204854&page=4

33) , 34) , 35)
aswracing of the XLFORUM http://xlforum.net/forums/showthread.php?t=15705

36)
aswracing of the XLFORUM http://xlforum.net/forums/showthread.php?t=15705&page=2

37)
Deimus of the XLFORUM http://xlforum.net/forums/showthread.php?t=67658&page=3

38) , 48) , 49) , 98)
aswracing of the XLFORUM http://xlforum.net/forums/showthread...ume#post110375

39)
bunny32 of the XLFORUM http://xlforum.net/forums/showthread.php?t=67658&page=3

44)
photo by Jörgen http://xlforum.net/forums/showthread.php?t=75740&page=9

45) , 46)
maru of the XLFORUM http://xlforum.net/forums/showthread...10#post3780510

47) , 55)
Hippysmack of the XLFORUM http://xlforum.net/forums/showthread...23#post5757523

51) , 104)
Jorgen of the XLFORUM http://xlforum.net/forums/showthread...d+valve&page=7

52) , 53) , 57) , 58) , 59) , 67)
Hopper of the XLFORUM http://xlforum.net/forums/showthread...chest+breather

56)
1960 HD FSM pg 3a-15

60)
HD Service Bulletin #M-848 dated April 9, 1982

61) , 64)
FoxsterUK of the XLFORUM http://xlforum.net/forums/showthread...ht=wet+sumping

62)
photo by Phillober of the XLFORUM, labeled by Hippysmack http://xlforum.net/forums/showthread...64#post3345764

65)
photo by DK Custom of the XLFORUM http://xlforum.net/forums/showthread...582019&page=11

66)
photos by Bored now of the XLFORUM, annotated by Hippysmack http://xlforum.net/forums/showthread...87#post5761087

68)
bunny32 of the XLFORUM http://xlforum.net/forums/showthread.php?t=15705&page=2

69)
Deimus of the XLFORUM http://xlforum.net/forums/showthread...=67658&page=18

70)
electronbee of the XLFORUM http://xlforum.net/forums/showthread...+valve&page=10

71)
photo by electronbee of the XLFORUM http://xlforum.net/forums/showthread...+valve&page=10

72)
photo by Bluto of the XLFORUM http://xlforum.net/forums/showthread...90#post5761290

73)
Photo by goblin_dust of the XLFORUM http://xlforum.net/forums/showthread...umping&page=23

75)
aswracing of the XLFORUM http://xlforum.net/forums/showthread.php?t=20871

76)
chart by aswracing of the XLFORUM http://xlforum.net/forums/showthread.php?t=20871&page=2

77) , 94)
aswracing of the XLFORUM http://xlforum.net/forums/showthread...1946516&page=4

78) , 79) , 80)
photo by aswracing of the XLFORUM http://xlforum.net/forums/showthread...1946516&page=4

81) , 82) , 83)
chart by aswracing of the XLFORUM http://xlforum.net/forums/showthread...1946516&page=4

85)
NRHS Sales of the XLFORUM http://xlforum.net/forums/showthread...+guide&page=31

86)
jrclark19 of the XLFORUM http://xlforum.net/forums/showthread...+guide&page=31

87)
http://xlforum.net/forums/showthread...+guide&page=31

88) , 89) , 90) , 91) , 92) , 93)
photo by cjburr of the XLFORUM http://xlforum.net/forums/showthread...+guide&page=31

95)
maru of theXLFORUM http://xlforum.net/forums/showthread...d+valve&page=6

97)
chevelle of the XLFORUM http://xlforum.net/forums/showthread...1204854&page=3

100) , 102)
Dr Dick of the XLFORUM http://xlforum.net/forums/showthread...1204854&page=2

101)
maru of the XLFORUM http://xlforum.net/forums/showthread...d+valve&page=7

103)
IronMick of the XLFORUM http://xlforum.net/forums/showthread...1332902&page=3

105)
Deimus of the XLFORUM http://xlforum.net/forums/showthread...107#post841107

106)
Gord of hpacademy.com https://www.hpacademy.com/forum/off-...y-sump-systems

107)
dieselvette of the XLFORUM http://xlforum.net/forums/showthread...107#post841107

108)
photo by WestJC7745 of the XLFORUM http://xlforum.net/forums/showthread.php?t=1971672

109)
photo by meherdad_it of the XLFORUM http://xlforum.net/forums/showthread...hreadid=944843

111)
Deimus of the XLFORUM http://xlforum.net/forums/showthread.php?t=87313

112)
Hippysmack of the XLFORUM http://xlforum.net/forums/showthread...971026&page=28

113)
photos by cootertwo of the XLFORUM http://xlforum.net/forums/showthread...hreadid=148936

114)
bustert of the XLFORUM http://xlforum.net/forums/showthread...el#post5750657

115)
Toejam503 of the XLFORUM http://xlforum.net/forums/showthread...el#post5750657

116)
Deimus of the XLFORUM http://xlforum.net/forums/showthread...umping&page=21

117)
Hippysmack of the XLFORUM http://xlforum.net/forums/showthread...94#post5763694

118)
ryder rick of the XLFORUM http://xlforum.net/forums/showthread...1904589&page=4

119) , 124)
https://www.gzmotorsports.com/why-use-vacuum-pump.html

120) , 121) , 122) , 123)
https://www.dragzine.com/tech-storie...en-horsepower/

I'm often at a loss to explain why I'm seeing what I'm seeing. I can only report on what I'm seeing and often speculate as to the cause or reason for what I'm seeing.
What I'm seeing has been nothing but positive. No air bubbles or foaming in the tank and a slightly higher oil level in the tank. Lower head temps also seem to be a result.
The technical reason this occurred is probably more than my limited knowledge can explain. I DO know it's a positive result of one or more of 3 things I did. A better one way valve that defintely lowers or eliminates positive crankcase pressure, moving where this pressure exits, and installing a pump with better scavenging. Perhaps it's the combination of these that's made it work so well. IDK.
I'm not suggesting anyone do this based solely off my experience.

So far so good on the rocker cover leaks as well.

i find no fault with the stock system, working as intended. as before, i route the vent diff but i have no issues with the bag. maybe with some more miles, things could change but for now, it'll take all the flogging i give it.
perhaps phsyco-somatic? like the little train going up the hill, i think i can, i think i can when in reality, he could all along!!!

We know that the more air that is pulled into the engine, the higher the density of oil suspension = puking.
This is with an unlimited supply of air but intake thereof is based soley on the duration of upstroke.

It's interesting that the krankvent comes factory with an air gap (the spacer).
The design should allow a controlled amount of air in behind the closing of the valve.
This controlled amount of intake will delay the affect of upstroke.
As in it will take a slight longer to build vacuum.
Thus net vacuum produced will be less.
The less the vacuum at the point of downstroke, the higher the affect of positive pressure through downstroke.

A fast closing valve simply allows more vacuum to be produced on upstroke.
Thus lowering positive pressure on downstroke giving better ring seal.
But better ring seal yields less blowby to help with scavenging.

So Gunner I'd deduce that your engine sounds better due to better ring seal from the lower controlled intake of air during breather valve closing.
You can install a clear return line temporary to actually see what's coming out of the sump and into the tank to check aeration.

I forgot ask.
What caused this?

Idk. You tell me. Every time I pulled a cover to fix a leak, I found something like that. Obvious damage that explained the leak. I assumed it was too much crankcase pressure. That got me looking into the breathers and found they weren't sealing out air for shit. And here we are.

Morning Hippysmack, don't feel rejected, we are separated by an Ocean and many time zones. And as I told you, I also am in the middle of major building work.

Surely, that depends on the pressures involved. If there is a sufficient negative crankcase pressure it could overcome the scavenging but Harleys don't
run like that. Because of the piston configuration oil a Harley they will have alternating positive and negative pressure similar to a single cylinder engine.
Take your scenario; as the pistons fall they compress the volume of air contained in the crankcase which contains oil mist and this air has to go somewhere.
If the engine breather does not vent these pressure spikes, the air is likely to find its way out of the engine via the scavenging which increases aeration.
So you end up with proportionally more froth in the oil tank and hence less oil. This is a simplified, as the movement of air will be effected by blowby,
revs harmonics, how airtight the engine is and scavenge capacity. What I think HD did was to progressively ensure that the air oil mist could be recirculated
in the lubrication system to minimise hydrocarbon emissions, albeit with a significant loss of BHP.

Have read of this summary for instance:
https://www.enginelabs.com/tech-stor...d-air-control/

Here is the Hayden patent (which also explains why they have the ring on their valve).
https://patents.google.com/patent/US5881686A/en

As I explained, I don't think the 'ballon' test is a good method to test air flow as it introduces too much back pressure for the PCV. You would need a flow gauge which I don't have.

Here is a pragmatic approach: if you get excess oil mist down your leg, gaskets that are oil misting or notice that the oil tank is filled with foam, try renewing the umbrella
valves (not easy on an the 86-90 engine) or replace them with a proprietary valve and see if it helps; like 60Gunner and I did.

It's all good.