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Old 04-15-2015, 02:22 PM   #1
Aircoolio OP
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Seeking crankcase vacuum...

Looking for ways to get lower crankcase pressures. Has anybody out there implemented a KrankVent to an airhead? Either in place of or in series with the breather valve (disc or reed)?

http://www.et-performance.com/index....products_id=87
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Old 04-15-2015, 03:06 PM   #2
Solo Lobo
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I don't think that the stock system provide any significant impediment to crankcase pressure escaping... perhaps someone who races can chime in.

removing the stock valve and replacing it with something else may provide some marginal gain, but would it really make any significant impact on the functioning of your bike?
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Old 04-15-2015, 06:38 PM   #3
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So this is supposed to vent the blow by gases and collect the condensate, or oily mess, in a can outside the engine? In the process it creates a vacuum or negative pressure in the crankcase? And it only costs $95.

What could go wrong? I want one. (I will admit to having bought several versions of other snake oils at times)

More info.

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Old 04-15-2015, 07:47 PM   #4
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I found my 900 engine used to fill the bottle on the racebike over time, but the 1000cc does not...unless I fill the oil near max.
I fitted a Mikes XS Yamaha PCV to my Commando and it works well, no longer have ( as much) oil trying to escape.
I think with a good valve you reduce the pumping losses of 1000cc going in and out...?
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Old 04-15-2015, 09:47 PM   #5
Rob Farmer
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The earlier bikes had the awful disc breather that caused lots of breathing issues and caused lots of oil misting round gasket problems as the engines clocked up the miles. Air was noisy as well. Fitting the later reed valve breather cured most problems
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Old 04-15-2015, 10:01 PM   #6
Bill Harris
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Aww, the old breather valve is so quaint. Here's the best description I've heard:

Quote:
I like the noise.

Sometimes it sounds like a long orgasmic sigh after a particularly good run, and I just have to light a cigarette and pat a jug with appreciation.

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:)

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Old 04-16-2015, 12:47 AM   #7
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As well as the change to the breather valve, BMW fitted a deeper oil sump to increase crankcase volume.
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Old 04-16-2015, 12:50 AM   #8
disston
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I too miss the Turkey Valve. Gooble Gobble.
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Old 04-16-2015, 01:03 AM   #9
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Quote:
Originally Posted by Bill Harris View Post
Aww, the old breather valve is so quaint. Here's the best description I've heard:


"I like the noise.

Sometimes it sounds like a long orgasmic sigh after a particularly good run, and I just have to light a cigarette and pat a jug with appreciation".

Airbear
Boxerworks Forum


:)

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Old 04-16-2015, 04:26 AM   #10
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Oh really?



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Old 04-16-2015, 05:01 AM   #11
bmwrench
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Quote:
Originally Posted by Aircoolio View Post
Looking for ways to get lower crankcase pressures. Has anybody out there implemented a KrankVent to an airhead? Either in place of or in series with the breather valve (disc or reed)?

http://www.et-performance.com/index....products_id=87
This is a fine example of hyperbole. Their amazing device is a power brake check valve. A one way valve does wonderful things for bikes without one, but the reed valve in our bikes does exactly the same thing. If you want to lower crankcase pressure-after making sure you have good ring sealing-get a vacuum pump commonly used on drag race multi-cylinders.
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Old 04-16-2015, 06:27 AM   #12
Aircoolio OP
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The KrankVent does sound too good to be true, which is why I was hoping there was somebody who's tried it already. Maybe I'll be the guinea pig...

I'm inspired to pull stronger vacuum downstream of the breather valve by that old "King of the Boomers" article: "To eliminate as much as possible crankcase pressure losses, Gietl has run a large flexible line from the case breather to a foam-filled box under the seat. Atop this box is a row of reed valves. The case quickly pumps itself down through this array, and at high speeds, an exhaust aspirator adds its suction to the effect. There was power to be had here, and Gietl has helped himself."
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Old 04-16-2015, 06:51 PM   #13
bmwrench
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I've used a BMW brake check valve (mentioned above) on Norton Commandos, and it made a world of difference, but their original breather was simply an open hose.
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Old 04-17-2015, 06:20 AM   #14
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Some of the differences between early 70s Nortons and airheads make you realise why the airheads were such premium priced products compared to the Nortons and the other Brit bikes.
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Old 04-18-2015, 12:24 PM   #15
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Don't know about the product listed at the top of this thread, but I saw firsthand the improvements to large marine diesels by fitting aftermarket devices that were effectively vacuum pumps creating negative crankcase pressures. The claims or theory were that by maintaining slight and controlled negative crankcase pressures piston rings (compression and oil control) seated better and reduced blowby, oil consumption, and oil contamination. And they worked.

Don't know if any true vacuum devices have ever been created for small engines or bikes, though.
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