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Breathing on the KH

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Barry55KH

Posts: 240

Joined: Mon Jan 17, 2005 1:01 am

Location: Kirkland, WA, USA

Post Wed Jul 26, 2006 11:40 pm

Breathing on the KH

Breathing on the KH

I know how the KH is suposed to get the crank case pressure out by sending it along with the oil, up the breather tower. Where does new air come in from? They have no primary side breather, and it has to come from somewhere? If it does not, it might explain all the problems I have with rings.

Best regards,
Barry55KH
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xlr

Posts: 149

Joined: Thu Aug 05, 2004 12:01 am

Location: calif

Post Thu Jul 27, 2006 3:26 pm

hi what problem areu having with rings? on your cam cover you have a breather. most of the time if oil is coming out of breather your rings are bad. to much crankcase pressure.
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Barry55KH

Posts: 240

Joined: Mon Jan 17, 2005 1:01 am

Location: Kirkland, WA, USA

Post Thu Jul 27, 2006 7:57 pm

I am looking for where the air goes into the crank case? I know where it comes out. It has to come from some where. Thanks for your ideas.

Barry55KH
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44dwarf

Posts: 318

Joined: Mon Feb 06, 2006 1:22 pm

Location: north central Ma.

Post Fri Jul 28, 2006 5:32 am

Barry.
I far as I can tell it's all blow by air and the changing crank case volume due to piston rise and fall. If rings are well sealed air will go both ways from the breather.

However I'm far from an HD dry stump guro. All my dry stump work has been with 4cyl race cars where the scavange pump pulls 28 inch of vacum in the motor with lite thention rings

44dwarf
"Smok'in the competition NOT Tobacco"
"Transplant organs, Don't bury them!"
Why dwarf? 5/8 scale race cars! http://www.dwarfcarracing.com
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Barry55KH

Posts: 240

Joined: Mon Jan 17, 2005 1:01 am

Location: Kirkland, WA, USA

Post Fri Jul 28, 2006 9:02 am

I got the same expaination from Hans, well almost. Thanks 44Dwarf, that makes it a lot clearer.

Hans said, "Barry, the breather has several functions. First one is to keep the
pressure in
the crankcase low. Otherwise if both pistons are down, you would have
say 2 atmosphere
pressure in the case. This could possibly break the cases and might
blow oil thru
seals. What you need for this, is a breather that opens momentarily
when both pistons
are close to the lowest position.
If you are at idle, the situation is close to this.

When you open the throttle, some gas will start leaking past the
pistons. This is
sometimes called blow-by. This gas has to get out thru the breather.
This now requires
a sizeable opening but still much smaller that the HD size, and that
opening has to
remain open long enough. Timing is still basically as above, but you
advance the
timing a few degrees since gasses always lag a bit with respect to
the mechanical
movements." (Per Hans.)

Thank you all!

Best Regards,
Barry55KH
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mike100m

Posts: 51

Joined: Fri Jul 23, 2004 12:01 am

Location: felton,Ca.USA

Post Tue Aug 08, 2006 5:03 pm

On our KR race motor I blocked off the stock breather and installed a 5/8" breather on the timing cover with a baffle. At the end of the breather hose I have one way check valve that only lets air exit the crancase. While I have no way of measuring the crankcase vacumn or pressure,
I suspect its negative because the minor oil weepage around the lifter gaskets dried up. The point is, as Dwarf stated, you want as high a vacumn as possible.
Mike
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BREWSKI

Posts: 919

Joined: Sat Mar 27, 2004 1:01 am

Location: RENO,NV. U.S.A.

Post Wed Aug 09, 2006 7:09 pm

If you're talking about the breather tower on the pump.I fail to see how that would work on an everyday street bike,on a high rpm race ebgine possibly. On an average engine it would wet sump and cause more problems than it's worth.
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mike100m

Posts: 51

Joined: Fri Jul 23, 2004 12:01 am

Location: felton,Ca.USA

Post Wed Aug 09, 2006 8:47 pm

BREWSKI wrote:If you're talking about the breather tower on the pump.I fail to see how that would work on an everyday street bike,on a high rpm race ebgine possibly. On an average engine it would wet sump and cause more problems than it's worth.


I'm talking about the blocking off the breather at the front of the timing cover. The timed tower breather remains. What the check valve does is reduce the pumping action and related losses. This would be benificial on any motor.
The Ducati twins use this system without the timed breather.
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steph

User avatar

Posts: 630

Joined: Fri Feb 21, 2003 1:01 am

Location: belgium

Post Thu Aug 10, 2006 12:00 am

That's how Harley did the sportsters in '77, they had a one-way valve at the breather on the cover.
I don't have a partsmanual for the sportster at hand, so can't give a #.
Stéph
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BREWSKI

Posts: 919

Joined: Sat Mar 27, 2004 1:01 am

Location: RENO,NV. U.S.A.

Post Fri Aug 11, 2006 3:58 pm

Thanks for the info,wasn't aware that H-D actually did that on the later XL's. BREWSKI
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panic

Post Sun Aug 13, 2006 3:27 pm

Crankcase vacuum is satisfied by air flowing back through the open breather slots for about 50 to 60 degrees after BDC.
Higher RPM: longer delay, XR750 is open for 90 degrees.
Higher case vacuum = more pumping loss.
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mike100m

Posts: 51

Joined: Fri Jul 23, 2004 12:01 am

Location: felton,Ca.USA

Post Mon Aug 14, 2006 8:02 pm

panic wrote:Crankcase vacuum is satisfied by air flowing back through the open breather slots for about 50 to 60 degrees after BDC.
Higher RPM: longer delay, XR750 is open for 90 degrees.
Higher case vacuum = more pumping loss.



Higher case vacuum = more pumping loss.
Panic
Are you speaking of a loss of pumping or a loss of power from pumping?
Mike
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Tim 435

Posts: 741

Joined: Mon Sep 01, 2003 12:01 am

Location: Pa. , USA

Post Fri Aug 25, 2006 8:44 pm

Hey Mike, I was thinking about doing that, what brand check valve did you use ? part# ? thanks, Tim
Vintage roadracing, Class C, AHRMA # 335
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mike100m

Posts: 51

Joined: Fri Jul 23, 2004 12:01 am

Location: felton,Ca.USA

Post Sat Aug 26, 2006 1:18 pm

Tim 435 wrote:Hey Mike, I was thinking about doing that, what brand check valve did you use ? part# ? thanks, Tim


Standard #AV30, Borg Warner #CV-39, Auto Zone-Sorensen #779-2945.
I use it with a small K&N on the outlet side. I use the BW brand.
Mike
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Tim 435

Posts: 741

Joined: Mon Sep 01, 2003 12:01 am

Location: Pa. , USA

Post Sat Aug 26, 2006 8:39 pm

Thanks Mike, if it works out I want to attach one to the exit side of my catchbottle/breather..
Vintage roadracing, Class C, AHRMA # 335
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panic

Post Sun Aug 27, 2006 7:30 am

One of these days I'm going to make a strobe photo of a check valve at 5000 RPM.
You know, about 3000 RPM after it stopped working, and is stalled partially open doing nothing?
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mike100m

Posts: 51

Joined: Fri Jul 23, 2004 12:01 am

Location: felton,Ca.USA

Post Sun Aug 27, 2006 1:45 pm

Tim 435 wrote:Thanks Mike, if it works out I want to attach one to the exit side of my catchbottle/breather..

Tim
Just remember its important that the crancase be completely sealed in order for the check valve to work correctly. I sealed of the primary and trans via a crank seal and plugged the crancase to primary check valve.. I vent the trans and primary thru a hole drilled in the top screw in the primary inspection cover. Also I vent the oil tank to atmosphere thru a foam filter. And don't forget to have the breather timed correctly.
mike
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mike100m

Posts: 51

Joined: Fri Jul 23, 2004 12:01 am

Location: felton,Ca.USA

Post Sun Aug 27, 2006 2:06 pm

panic wrote:One of these days I'm going to make a strobe photo of a check valve at 5000 RPM.
You know, about 3000 RPM after it stopped working, and is stalled partially open doing nothing?


Panic
You may have a point with some of the ball type check valves if thats what you are refering to. What I'm talking about is a reed type that has very little mass and spring pressure to help close it. We are not talking about a very strong vacumm here,probably just a few inches of water. I don't think it would make any power difference but it calms the turbulence in the crankcase and helps with scavanging. A check valve would only show a power gain from better scavanging if the engine was prone to sumping, which would cause a power loss because of drag on the flywheels.When I drain the crancase after a race I only get 1 to 1 1/2 ounces of oil. And like I stated in a previous post it dried up the minor oil seepage around the lifter blocks which is an indication of a pressure change in the negative direction.
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Frankenstein

User avatar

Posts: 1551

Joined: Thu Jun 27, 2002 12:01 am

Location: Interlaken, NY USA

Post Thu Sep 21, 2006 6:00 pm

Maybe the reeds would be more efficient than balls at higher rpms. I know the BSA Goldstar went from the ball type of the M20 to a timed breather to keep crankcase pressures down, this was back in the mid '50's. I've lived it, the ball type wouldn't handle high rpms. Gives me a chuckle when these evo guys add them to their breathers.
Dr. Dick

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