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  #271  
Old 13 Hours Ago
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Yep, if we hadn't agreed to think about something else, I would have said this.


Blocking the breathers is bad juju.
But, in that case, the whole system will block up. The tank couldn't vent to the cam chest which would be pressurized so it'd just blow the oil cap.
But wouldn't it be oil pressure that did that, not CC pressure?
The scavenger is capable of providing more pressure than the pistons generate.

And it's not really the scavenger's job to separate the oil/air mist.
Oil moving between the cavities can't increase the air mixture if there isn't any to begin with.
So the answer to solving air/oil mix in the pump is to not let air get there to begin with.

Here is what I see when searching for a fix.

Dave76's oil pump conversion will fix the problem of the flailing 86-90 oil pump design.
Karling's oil pump mod will keep gearcase air/mist out of the pump.
aswracing has a mod for a Homemade Oil System Bypass in the pedia.
http://sportsterpedia.com/doku.php/techtalk:refil05a
This is a mod to address wetsumping at high revs "Wet sumping has been an issue on high rpm Sportsters for forever"
This should send excess feed pressure back to the tank.
Jorgen's filter pad mod along with Tore's idea of taking it back to the tank will keep bypass oil out of the sump.
And at the end of the day, you end up wetsumping anyway due to other conditions not addressed yet.

The breather system can be expanded.
Regarding the scavenger side,
The linked article suggests an inline oil separator in the return line.
It also pushes the scale of a commercial article.
One could pick it apart on a daily driver mentality.

Something tells me we're both after the last chicken leg on the plate and neither one of us realizes there is a separate pan in the oven.

I am in agreement that aeration is an inherent condition.
But the causes are numerous.

I'd think there is adequate air/oil separation in the Sportster engine, in the regards of proper engine breathing, if oil doesn't glob out the vent.
But engine breathing and oil frothing are two separate but intertwined ideas.
That's the designs we are given with the oil tank also designed to help separate the air and oil.
But the air inside the tank doesn't get there because of CC pressure alone.
There should be a variant oil level in the tank depending on many factors.
The air was there first. Then the oil was added.
If you add too much oil, there will be even less air.
The displacement of ambient air in the tank relies on the vent.
Without the vent, the system locks up.
It may be compounded due to air/oil separation once there.
In these drawings I used a syringe instead of the engine due to time.




When you fill the oil tank to the proper amount, the upper portion of the tank is occupied by air with the engine shut off.


So, if you are correct with your summation, the MoCo has already accounted for this condition.
And obviously, there are flaws with higher revs.
So one would could also summize that the MoCos design was not intended for such high revs.

I also believe higher pressure in the crankcase will equate to higher output at the breather.
I think the turbulence at higher revs contributes to oil frothing (air attaching to the oil) instead of the higher pressure simply taking over the oil line.

I agree that oil frothing is actually a condition of air bubbles 'attaching' the the oil.
But the word mix is decieving. I'm no chemist, but I don't get the idea of air 'dissolving' into the oil.
Oil and water isn't supposed to 'mix' but when they get together (with heat and turbulence), they make an imulsion.
I haven't noticed anything like that in my oil tank though.

I have only tested the triple digits, hope law enforcement's not reading this, but for the fun of it.
I also assume high revs in a daily driver are in the intermittent 4000-5000s.
Whereas race engines may see sustained rpms in the 6000-7000 range?
It's a different sort of turbulance in the oil system.
But either can result with air in the oil lines.
Daily drivers, I assume, would be more intermittent.
Racers will have more prolonged affects.

But, you're right. I sure am glad we called it quits.

edit:
From other threads I've read, most will accept the fact of aeration unless it's obsessive.
This changes, of course, for high performance applications.
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What are the real world results of the oil pump conversion?
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Quote:
in that case, the whole system will block up.
My tongue in check suggestion was for you to look inside your oil tank while you blocked the breathers.
That would imply the cap was off to vent air - hopefully briefly.
(I am truly sorry you have gone to so much trouble to explain the obvious ).

Quote:
So, if you are correct with your summation, the MoCo has already accounted for this condition. And obviously, there are flaws with higher revs.
So one would could also summize that the MoCos design was not intended for such high revs.
As I have explained, I 'think' the below piston design is potentially better as it should be able to react faster to
CC pulses and in theory vent more of the CC. The problems I have with the head breather
design is that it is convoluted, plus the increased likelihood of the elastomer hardening due to heat. But both
should work to a degree. You seem to have a knack of finding threads but I seem to recall a thread where someone
added a cam chest breather in their high capacity sportster - probably Yörgen. Tore also added a modified reed
valve to to his breather. And both redirected their relief valve oil back to the oil tank. This seems a more thought out
approach than adding an 07 pump to an engine not designed for the open drain port. It would be great if those
gentlemen could chime in.

Quote:
What are the real world results of the oil pump conversion?
The closest we have is what Jorgen reported. The open 07 drain port looses about 60% of the scavenging.
Hence, I decided against the 07 upgrade, plus I am lazy. So, I fitted a more efficient PCV valve - I noticed
the oil level in the tank sat about 5mm higher afterwards. It was my impression at the time that there was
less foaming in the oil tank but that is subjective and subject to so many variable. But the oil misting on the
rocker gasket stopped .........so that saved me a job!

Here is a post from Tore in the "breather 101" thread:
Quote:
I built my own foo-foo, a reed-valve from a 50cc two-stroke in a housing.
Those are designed to work on WERY high revs and with absolutely no leak back.
Notice we concur that the speed of the valve is important - particularly at higher revs. I also use a reed valve design
(ET performance). As the elastomer hardens in an HD umbrella valve, it presumably becomes less efficient at speed.

And here the same thread talks about using vacuum pumps to improve power in race engines.
http://xlforum.net/forums/showthread...reather&page=7

Note: I am not claiming that a simple PCV valve can do the same but it should assist by capping CC when it works properly.
http://www.nightrider.com/biketech/crankvent_test.htm

and from Rolli
Quote:
Its a ultra fast flutter valve. Sounds like a trumpet if you blow through.Located here:https://www.xs650shop.de/zylinderkop...ungsventil-uni
I tried different PCV's. None of them was fast enough to establish a proper crankcase vaccum which is important for our V-Twins.
The enginge is fighting against itself when pistons are moving down.
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