SuzukiSavage.com - CrankVent Test

DragBikeMike

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CrankVent Test
03/27/20 at 23:40:41

Hayden CrankVent Test

Back in October of 2019, I had some problems with my breather system. My cylinder base gasket failed. I thought the gasket failure might have been associated with a device called a Hayden CrankVent that I installed in my breather system.

I ultimately concluded that the gasket failure was most likely due to insufficient cylinder stud stress.

Now my motorcycle is back in business with a fresh top end. This post reports the results of my follow-up tests on the Hayden CrankVent.

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DragBikeMike Serious Thumper Offline SuzukiSavage.com Rocks! Posts: 4169 Honolulu	Re: CrankVent Test Reply #1 - 03/27/20 at 23:41:46 Here’s what the CrankVent looks like. It fits nice.
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DragBikeMike Serious Thumper Offline SuzukiSavage.com Rocks! Posts: 4169 Honolulu	Re: CrankVent Test Reply #2 - 03/27/20 at 23:42:34 I now have a liquid-filled compound gage. It is better suited to the high-vibration environment. Hey! Don’t be snickerin at my gage mount, it’s resilient.
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DragBikeMike Serious Thumper Offline SuzukiSavage.com Rocks! Posts: 4169 Honolulu	Re: CrankVent Test Reply #3 - 03/27/20 at 23:43:24 I connected the gage to the oil filler cap. I did not install the CrankVent, the breather system was open.
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DragBikeMike

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Re: CrankVent Test
Reply #4 - 03/27/20 at 23:44:24

I operated in this configuration for well over 500 miles while I was breaking in the new top end. For the break-in I used the standard technique of accelerating and decelerating. It was a continuous regimen of accelerate gingerly to 4000 rpm, and then chop the throttle and use compression breaking to bring engine speed down to about 3000. So, force the rings into the cylinder wall with combustion pressure, then pull oil up the cylinder using vacuum. The standard process.

Observing the compound gage quickly identified a repeatable pattern. As I would approach 4000 rpm, the gage would start moving into vacuum and settle in around 1.5” Hg. As I would decelerate, the gage would return to zero. With an open breather, the engine pulls a very slight vacuum as you accelerate at part throttle, and maintains a slightly lower vacuum (about 0.5” to 1.0” Hg) as long as the engine speed stays above 3800 rpm (or thereabouts). It pulls the highest vacuum when accelerating.

I could see that I did not have the ideal gage connection. Oil would accumulate in the gage line. I didn’t like that.

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DragBikeMike Serious Thumper Offline SuzukiSavage.com Rocks! Posts: 4169 Honolulu	Re: CrankVent Test Reply #5 - 03/27/20 at 23:45:11 So, I moved the connection to the exhaust valve cover. It had a similar problem but not as severe.
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DragBikeMike Serious Thumper Offline SuzukiSavage.com Rocks! Posts: 4169 Honolulu	Re: CrankVent Test Reply #6 - 03/27/20 at 23:45:49 I tried a new connection on the alternator cover. That worked good. The gage line stayed dry.
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DragBikeMike

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Re: CrankVent Test
Reply #7 - 03/27/20 at 23:46:51

All these different gage connections really didn’t make any difference. The gage always behaved the same. Accelerate gingerly and it would start pulling a vacuum as the rpm approached 4000. Decelerate and the gage would return to zero. The vacuum would plateau at about 0.5” to 1.0” Hg when I maintained steady rpm above 3800.

Once I was finished with the break-in I continued to run the open breather and observe the gage. Now I could go WOT. At WOT, the gage would remain at about 1.5” Hg, no more, no less. I was in the middle of carburetor testing, so I was able to observe the gage over & over. Go WOT and the gage held 1.5” Hg vacuum. It never moved in the pressure direction. Always vacuum.

Once I was satisfied that I knew exactly how the crankcase pressure behaved with an open breather, I installed the CrankVent. To be fair to Hayden, I must disclose that I modified their product (my old post gives the nitty-gritty). I don’t believe anything I did to the CrankVent would result in it not being able to pull vacuum.

With the CrankVent installed, the crankcase vacuum remained exactly the same. Accelerate gingerly and the gage starts to move into vacuum as the rpm approaches 4000. Decelerate and it returns to zero. Maintain rpm at about 3800 or more and the gage indicates a steady vacuum (about 0.5” to 1.0” Hg). Go WOT and the gage indicates vacuum (about 1.5” Hg). The gage never indicates pressure.

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DragBikeMike

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Re: CrankVent Test
Reply #8 - 03/27/20 at 23:48:29

Seat-o-da-pants was not much help. It kinda felt crisper with the CrankVent but you know how that goes. It’s a crap shoot.

One way to compare the CrankVent to an open breather was fuel mileage. Perfect, I was doin carb testing so I could see if the CrankVent improved fuel mileage. No such luck. The open breather got 59.2 mpg while the CrankVent got 58.1 mpg. I would say that’s a tie, within the margin of error.

I tried several timed runs to see if one configuration is faster than the other. The 2nd gear 4K to 7K times were exactly the same, 2.90 seconds
I thought this contraption had potential. I was wrong. My motorcycle runs exactly the same with or without the CrankVent. It’s a wash.

Interesting Observation: Early on, when I was using a different vacuum gage on a higher compression engine, the crankcase would go into pressure when I went WOT. As it approached 7500 it would be pressurized as much as 2 psi. That’s a small number, but it still indicates that I didn’t have an ideal ring seal. With the new ring set, the crankcase pressure remains a slight vacuum all the way up past 7K (with or without the CrankVent), and it pulls the highest vacuum ( a blistering 1.5” Hg) when the engine is under load.

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DragBikeMike Serious Thumper Offline SuzukiSavage.com Rocks! Posts: 4169 Honolulu	Re: CrankVent Test Reply #9 - 03/27/20 at 23:52:15 This old post has the details on the gasket failure. http://suzukisavage.com/cgi-bin/YaBB.pl?num=1570415428 This old post has the details on the stud stress. http://suzukisavage.com/cgi-bin/YaBB.pl?num=1576269113/12#12 Hope you find this post beneficial. Knowledge is power. Stay well in these troubled times. Mike
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justin_o_guy2 Serious Thumper Offline What happened? Posts: 55279 East Texas, 1/2 dallas/la.	Re: CrankVent Test Reply #10 - 03/28/20 at 04:12:56 Knowledge is power.. As much knowledge as summa you guys have Your bikes otta run 150..
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Armen Serious Thumper Offline Half-Witted Wrench-Jockey from Jersey Posts: 1431	Re: CrankVent Test Reply #11 - 03/28/20 at 20:57:13 Gotta say, I'm confused about the motor running negative pressure in the bottom end with the stock breather with no one way valve. How does that happen?
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DragBikeMike

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Re: CrankVent Test
Reply #12 - 03/28/20 at 22:47:00

Good question. I pondered that for a bit. Here's what I think.

The first couple of down strokes nothin is stopping the piston from forcing the air out of the crankcase. On the upstrokes, all we have is atmospheric pressure trying to fill it back up again. There's a screen in the way too. So forcing the air out is a piece of cake, while forcing the air back in is a slower process with significantly less pressure to work with. So in normal operation, more air is forced out than is returned. So you end up with a very small vacuum.

It's all I can come up with. I spent a lot of time watching that gage. I even changed it's orientation to make sure that the needle wasn't moving due to inertia. It always behaved the same, always a slight vacuum on acceleration. It's evident that the cylinder pressure has something to do with it. Didn't behave the way I thought it would. Shocked

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Armen Serious Thumper Offline Half-Witted Wrench-Jockey from Jersey Posts: 1431	Re: CrankVent Test Reply #13 - 03/30/20 at 07:52:52 So DBM, on a motor with less than perfect ring seal (many of the bikes on the road), the crank vent makes a difference. With really good ring sealing, not so much. Am I reading that right?
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DragBikeMike

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Re: CrankVent Test
Reply #14 - 03/30/20 at 15:25:22

Armen, no I don't think the CrankVent will work better on an engine with blow-by. Maybe I should say I don't know if it will work better.

On that old high-compression engine, I observed the crankcase pressure going up to about 2 psi at high rpm (I have a vid if you are interested). That appears to be the result of blow-by past the rings. Did the pressure build simply because of blow-by, or did the pressure build because of inherent restriction in the Crankvent contraption?

If you examine your CrankVent, I think you will agree that it is restrictive. I'm sure yours is even more restrictive than mine because the mods I did to mine increased the radial clearance between the umbrella valve and housing.

Unfortunately, I blew up the gage before I had the chance thoroughly test between open-vent and CrankVent.

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