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Author Topic: oil blow by  (Read 3703 times)

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Offline zajaco

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oil blow by
« on: July 28, 2014, 11:10:43 pm »
Has anyone experienced oil blow by (oil leaking out of the crankcase breather into the air filter) after installing a high flow filter kit?  I had my first experience with it this past weekend after some long riding.  I had a nice puddle directly under the filter on top of the crankcase.  My oil level is right at the very top of the hash marks on the dipstick.  I hope the fix is as easy as a little less engine oil (middle of the dip stick).  Any thoughts?
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Offline ShakerNorm

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Re: oil blow by
« Reply #1 on: July 29, 2014, 01:02:22 am »
Zaj - did you check your oil when it was on the kickstand or were you holding it vertically?

The manual says you have to check it when you're holding it vertical. If it's on the stand it will read higher than it actually is.

Yeah - I'm kind of shaking my head at the logic, too, but if you raise or lower your bike's suspension, it'll change the angle the bike sits at when it's on the kickstand and will make the oil level inaccurate.

OKAY - on to your actual problem..... One of the ports to the air filter is your crankcase breather hose. I expect that is where the excess oil is from.

With the stock filter, the oil is still vented, but is hidden inside the filter case.

I also seem to remember that it is vented inside the filter. The stock filter is so restrictive that it creates a slight vacuum and helps pull that oily air back into the engine to be burned. Your new higher-flowing filter isn't quite as good at that.

The cure? Not too sure...
Any suggestions?
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Offline u-bolt

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Re: oil blow by
« Reply #2 on: July 29, 2014, 05:25:53 am »
another confusion measuring oil level ... as Norm says first the bike must be upright,

and then unscrew the filler /dipstick, the level you see will be reading high, wipe it put it back in against the thread but not screwed in and have another look, this is the level that matters.

I'd say a little oil from the crankcase breather is normal, but not enough to noticeably affect oil level.
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Offline Super Sneaky Steve

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Re: oil blow by
« Reply #3 on: July 29, 2014, 08:17:47 am »
I think you may have too much oil in your case but even at normal levels you'll get some oil in your box.

Unless you do the SSS crankcase breather mod!
https://www.yamahastarbolt.com/technical-discussion/crankcase-breather-reroute/

 ;D
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Offline zajaco

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Re: oil blow by
« Reply #4 on: July 29, 2014, 08:37:43 am »
I checked the oil per the manual.  Using a motorcycle jack to level the bike out (wheels still touching the ground) I pulled the dip stick out, wiped it off and set it back in without engaging the threads.  Using that method I was reading at the highest hash mark.  I just did a 1200 mile oil change and instead of putting the 4.23 quarts in, I put in an even 4 quarts.  Oil level looks ok.  If I still am getting drips out of the filter I may reroute it or plug the vent line.
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Offline ShakerNorm

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Re: oil blow by
« Reply #5 on: July 29, 2014, 09:28:02 am »
Rerouting it is OK, but don't plug the line - the crankcase needs to be vented.

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Offline collins50235

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Re: oil blow by
« Reply #6 on: July 29, 2014, 01:13:15 pm »
I noticed this after changing to the Hard Times kit. It was after about 90 or so miles. However I had never oiled a K&N filter before an I think my issues was a touch of oil mixed with a lot of excess filter oil. Could that be what your seeing?


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2014 Bolt - Vayne

Offline zajaco

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Re: oil blow by
« Reply #7 on: July 29, 2014, 01:31:59 pm »
Quote from: ShakerNorm on July 29, 2014, 09:28:02 am
Rerouting it is OK, but don't plug the line - the crankcase needs to be vented.

Sent from my GT-S5830D using Tapatalk 2

Roger


Quote from: collins50235 on July 29, 2014, 01:13:15 pm
I noticed this after changing to the Hard Times kit. It was after about 90 or so miles. However I had never oiled a K&N filter before an I think my issues was a touch of oil mixed with a lot of excess filter oil. Could that be what your seeing?


Sent from my iPhone using Tapatalk

I am using the same kit actually.  However, it was defiantly engine oil and I had a good puddle going on the crank case and a fair amount of wind blown oil streaks going on the upper section of the rear pipe.  I'd really have to try to oil my filter that much  ;D
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Offline zajaco

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Re: oil blow by
« Reply #8 on: August 02, 2014, 01:30:08 pm »
Well... it happened again.  It was raining yesterday when I rode the bike home so I didn't notice the oil streaks till today.  Again, I have a pretty decent oil puddle and slick going.  You can kinda see it in the pics below even though they are a bit dark.

My working theory is the high flow filter is causing low pressure directly in front of the breather.  I think if the breather were moved farther back on the adapter plate (closer to the riders leg and farther away from the incoming air) I wouldn't have this problem.  As I'm typing this I'm wondering what is stopping me from flipping the adapter plate to that position.  :o

What I did was get a PVC elbow from auto zone.  I trimmed the end a bit so it would fit behind the filter element.  My thinking is that reorienting the vent line in relation to the incoming air will lessen the low pressure it experiences and hopefully keep the oil where it belongs.

After performing this mod I saw a post from cefox where he puts an inline fuel filter in the breather hose to resolve this issue.  If my pcv elbow does not work out that is my next course of action.
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Offline buckeye bolt

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Re: oil blow by
« Reply #9 on: August 02, 2014, 05:15:23 pm »
I am not sure I can help or not but I will offer a guess. The hose you are having troubles with is supposed to supply clean filtered air into the low pressure side of the crankcase from the filter box. Air is not supposed to flow from the crankcase to the filter box like you are experiencing. Here is where the guessing starts and if I weren't so lazy at this time I would go out and trace some hoses so maybe you can if you want to. I think the hose coming in to the top of the left hand side of the intake manifold in your top pic above is supposed to pull air out of the high pressure side of the crankcase. If you install the low restriction breather then the vacuum pressure in the intake manifold drops when the throttle is in a open position more than it would with a higher restriction breather. The more RPMs the more the crankcase pressure. If the pressure is not sucked up from the intake it will find its way into the breather hose. Not sure how you can cure the issue. Need think time. Enjoy the ride.
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Offline ShakerNorm

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Re: oil blow by
« Reply #10 on: August 02, 2014, 07:14:24 pm »
Actually, Buckeye -
Air moves both in and out of the crankcase with the movement of the pistons. As they go up and down, the volume of air in the crankcase changes and forces the air to pulse in and out of the breather.

The splashing of the oil inside the crankcase causes the oil to mist, and as the air flows in and out of the breather, it takes some of that mist with it, and THAT is what's causing his problem. On your car, this air goes through the PCV valve and back into the top of the engine (usually the valve cover) where the air is unpressurized and the oil is recirculated back into the engine. Unfortunately, we don't have that option.

I have a K&N on mine, and notice that my filter gets quite oily very quickly, too.  I've already washed it twice this summer.

I think that cefox's fuel filter idea is actually a REALLY good one - it should stop the oil mist from getting into the air filter, while still allowing the air to move as it needs to.
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Offline buckeye bolt

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Re: oil blow by
« Reply #11 on: August 02, 2014, 09:31:45 pm »
In the car; The gasses in the auto engine get mixed with the fuel and get burned. When the PCV valve can not suck it all up it goes to the breather. I've had enough worn out 396s to know this problem. 

In the bike; The volume of air would remain the same because the two pistons move opposite. They displace the air equally so as one goes up and one goes down, no change in volume of space in the crankcase. The pressure does pulse because of the amount of air that slips past the rings during the compression and power strokes of the pistons, not the movement of the piston. I assumed the bike would have a similar type of system, Your going to make me look. LOL I have my virago apart maybe it is easier to review. May be different though.

Lets work this out. I like this type of discussion.
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Offline ShakerNorm

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Re: oil blow by
« Reply #12 on: August 02, 2014, 10:28:43 pm »
But this is NOT a 90* engine, it's a 60* difference, so the pistons are NOT in synch when they go up and down, and there is a change in internal volume. Not as extreme as say my XS650 parallel twin (both pistons go up and down at the same time - so LOTS of pulsing), but it does change. And, as you say, there is blowby always adding more air to the air that's already there.

Seems Yamaha is of the belief that "if it's not broke, don't fix it", since a lot of the systems are very similar to my old XS (1979... but the engine was designed originally in the 50's). 

But.... I do think that the filter in the line is probably the best cure to come out, so far - I think I'll be trying it, myself...  Now - if I can just find that old fuel filter that I had for the XS.....
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Offline buckeye bolt

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Re: oil blow by
« Reply #13 on: August 02, 2014, 11:07:36 pm »
Indeed the homework was not done and I failed the test. It would have to be opposed cylinders for the pressure to act as I stated. A quick look at the Virago looks like it breathes from the top of the head in the cam cover area. Looks like the Bolt breathes from the block behind the cylinders. Only other option I can think of other than the filter trick would be a catch can or vapor can to condense the vapor and return it to the block or dump it when it gets full.  Something like we used on our alcohol go-karts.
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Offline ShakerNorm

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Re: oil blow by
« Reply #14 on: August 03, 2014, 04:42:36 am »
Wouldn't say you failed anything, Bro.... But I'm an aircraft mechanic and had to learn all that crap.... LOL.

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