Another oil mist problem & slobber stoppers

[SamR47]

Originally Posted by John Harper

Yes, and seems so simple, why did Harley not do that? Just a slight change to the middle cover casting. If that solves the issue, of course.

I have noticed running a lower oil level on my '91 shows less oil through breathers. Tomcatt's advice seems solid. I've been experimenting and have seen a correlation so far.

John

I think the MoCo, though, the design is good since the drain holes are in the highest points of the heads (V), and the gravity will take care of it.

Now, why did MoCo not fix it since the issue become more noticeable? Well, it is HD, and who knows!

Just by looking at the Milwaukee-Eight engine oil pump issue 2017-2019, a severe issue, and how did HD waited for full 2 years until they fix it!

[Hippysmack]

It's easy to say Harley ****ed up with the marks on the stick and I've heard that argument already.
But I've weaved in and out of some of other so called ****ups to find they new what they were doing.

[John Harper]

From what I've been seeing as I've lowered my oil level to the lower mark, is that there is less weep from my rear SE backplate spacer. I usually see a small sheen of oil after a ride, not even a drop, but being OCD, I see that stuff. With less oil, less sheen. I still seem to get a bit of oil on bottom of ham can, but that also seems normal for these engines. IDK. On the other hand, when the oil level was up it still was not much of a seep. But, using only 2.5 quarts means I can split a 5 quart jug of VR-1, which is another bonus!

I'll never live to put enough miles on to prove internal v. external breathers, which is better. Likely insignificant.

And, we're the tiny percent of owners who even notice the issue, much less care.

John

[Hippysmack]

Oil/air separation actually means collision. We've seen that in 1957 to present designs.
The breather design with the umbrella also uses collision.
But the umbrella is the LAST collision point in the system.
HD knows all of the oil will not stay below the umbrella, thus the little drain chamber.

I'm gonna try and make this quick....er than usual.
The 45 piston design is THE cause of higher than other engine (push/pull) crankcase air.
That little hole in the drain chamber is open to atmosphere.
But it's so small (by design) that not enough air can get pulled back in the engine before the next downstroke.
The problem I have with enlarging that drain hole is due to the possibility of MORE atmosphere being pulled in during upstroke.
The system is design to have a slight vacuum.
More air into the motor lowers that vacuum design.
79-present Sportsters have a drainback hole.
57-90 motors breath from the cam chest, not the heads.
So the higher design is not necessarily the bees knees, just different.
When these bikes leave the factory, they don't puke oil. What did they need to fix?

[Hippysmack]

That's exactly all I have seen period regarding oil tank level...… because it works.
No other reason.
But you are allowing less cooling factor when lowering oil so there is a drawback to that practice.

Lower oil level=less oil in the sump to be picked up into suspension to rise out the breather?
Maybe check for pinched vent line or some rubber hoses can either implode or shrink inside, lowering flow.
Maybe check to see if you have more blowby = compression check.
Maybe check crankcase pressure to see if you have too much vacuum.
Vacuum helps pull oil in suspension in the crankcase.
Maybe check the rocker cover bolts/gaskets for leaks.
Oil can get out but air can get in.
I can maybe this for a couple pages.
But none of that is usually considered by most.

That's why I consider lowering the tank and others as bandaids.

[Hippysmack]

I guess I'm looking for more why than a fix.

salmanmr,
Why, would you think, that there is more oil in that chamber that can drain out?
It has to be an assumption that the oil is pooling up in that chamber and overflowing to the exit air hole.
If you raise that exit hole level, will MORE oil pool in that chamber?
If so, that's more hot oil to mix with the outgoing air and blow out the vent.

On upstroke, the vacuum pulls oil down to the boxes thru that drain hole.
It's too small for gravity to flow oil.
So if you are not making enough vacuum, then yes, oil can pool in the chamber and blow out the vent.
In that case, it's not the exit hole level, it's too little vacuum.

So you see, I'm very interested in hearing how this mod works out for you.

Edit:
Notice the instructions say to also "replace the umbrellas".
My contention is if you replace the umbrellas and not add this mod, you may find the problem goes away or subsides dramatically.
If the maker of the barrels has more data on the ill gains of a used umbrella, they should share it.
I've certainly measured gains from replacing them.
But you can replace them, add the Slobber Stoppers and if you have an air leak around the cover bolt(s), you'll still churn oil.

I'll also add, I have found nowhere in the HD FSMs that give inspection or replacement intervals for the umbrellas.
So how did it come to pass that the maker of the SSs decide it was a requirement along with their product?

I think I would just use the old umbrellas with the Slobbers and see what happens, then replace with new to see the difference.
I may try this mod too just for the knowledge.

[SamR47]

Great analyzing and analogy on how this mod works and how the oil/air mist occurs in engine heads.

Unfortunately, I don't have that much mechanical depth, and I can't fully imagine the engine vacuum functionality aspects.

After reading your inputs, I think HD purposely made the heads with large tolerance in oil plumings. And I think, the reason for doing so, is to have it as a safety mager against over fulling oil, which puts the umbrella under constant pressure to decides who stays in and who out! Likewise, the oil fill rubber cap!

following the same logic with large tolerance in oil plumings, I think, the umbrella design was a uniform design to accommodate 883, 1200, and other EVOs engines with a high compression ratio! (seems the umbrella replacement part number is the same across all models)

Maybe the solution is way easier and simpler than we all thought! All we need is a new umbrella, made from a better material!
Not made from a stiffer material, but made from a different material thickness to control the pressure/vacuum airflow resistance/build-ups, and of course, withstand constant heat cycles.

I quickly searched to see if I could find an umbrella valve seal made with high-performance/better material, and there was none.
V-Twin Manufacturing, Genuine James, and HD MoCo all looked the same to me!

God, I love theories!

[Hippysmack]

I need to clear up a few things.
Oil pump pressure has NOTHING to do with oil coming out the breathers or going to the rocker boxes for that matter.
All new umbrellas are soft rubber.
They get hard due to heat in the boxes over time.
They are supposed to close fully on every piston upstroke (suction in crankcase).
Oil pump return pressure is relieved in the tank via the vent back to the camchest.
This is air/oil mist (not like in a handful of oil).
Crankcase, gearcase, oil tank and rocker boxes all share the same air space.
Air/oil mist (not a handful of oil) is used by design to blow around and lubricate stuff.
It's the final separation at the umbrellas where the MoCo wants oil to go back into the motor and excess air out the heads.

The inlet/outlet sizes are by design.
The umbrella is (in theory) getting blown and sucked on at the same speed as the engine.
But the truth is, there is a point at which the engine acts faster then the umbrella does.
So the umbrella kind of floats.
Due to the drainback hole, other forces are at work also from outside upon the umbrella.

Piston size will add/subtract to the volume of air that has to be maintained in the bottom end, yes.
The only difference I've found in the replacement umbrellas is color(same part for all 91-03 Sportsters).

Since there are no replacement intervals for the umbrella in service manuals, people don't think or sometimes believe they are a concern.
So they go out and buy Brand X cause they say their product is THE FIX.
It's actually kind of funny that they say to replace the umbrella along with the Slobbers.
Guaranteed noticeable difference by default of the new umbrellas.
They can't go wrong with that mentality.

Now dangit, I wasn't trying to talk you out of the Slobbers, just didn't want you walking in blind.

[Hippysmack]

Originally Posted by salmanmr

God, I love theories!

Most don't think kindly of what they can't see or feel.

But if it ever get bored, here is the Evo Crankcase Pressure and Engine Breathing in the Sportsterpedia.
http://www.sportsterpedia.com/doku.p...:ref:engmech04