back pressure
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Tourer
Joined: Oct 2009
Posts: 407
Likes: 2
From: Bixby Oklahoma
back pressure
I have been disappointed with my bike dripping oil from the air filter - an 09 Ultra 103/251 cams/ Zipper Air filter, V & H power duals and Monter Ovals. Have gotten lots of opinions, including I get fuel reversion from the cam holding the valve open too long, tried Doherty mist free, could be over full crank (running a quart low now) and still blows.
So the latest suggestion is build some back pressure into the exhaust since it might flow "too good". The first suggestion was to plug some of the exhaust port holes in the last few inches of the Monster Oval that has seven or eight or so rows of holes in the last few inches of the muffler pipe. So what if I took the muffler off and tacked a washer onto a bolt head and put it at the joint between the headers and the muffler. Maybe a 3/4 inch washer on a bolt long enough to center the washer in the pipe? Anyone buy this suggestion or have tried it??
thanks
So the latest suggestion is build some back pressure into the exhaust since it might flow "too good". The first suggestion was to plug some of the exhaust port holes in the last few inches of the Monster Oval that has seven or eight or so rows of holes in the last few inches of the muffler pipe. So what if I took the muffler off and tacked a washer onto a bolt head and put it at the joint between the headers and the muffler. Maybe a 3/4 inch washer on a bolt long enough to center the washer in the pipe? Anyone buy this suggestion or have tried it??
thanks
Outstanding HDF Member
Joined: Feb 2007
Posts: 2,837
Likes: 50
From: usa
My 09 Classic stock motor with SE/AC an HD download seems to drip less with 4" Rineharts on than when I had the 2011 CVO slip-ons on.I would think that the CVO pipes had more back pressure than the Rineharts.
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Tourer
Joined: Oct 2009
Posts: 407
Likes: 2
From: Bixby Oklahoma
I would have thought the same, I guess I will try something to make the back pressure increase to see if it helps........she pukes quite a bit and the faster we go the worse it is, pretty tired of it
Elite HDF Member
Joined: Nov 2010
Posts: 3,846
Likes: 171
From: Simi Valley, CA
Personally I don't see how increasing exhaust back pressure could eliminate (or decrease) oil in the air cleaner.
Think about it.
Oil in the air cleaner is coming from the crankcase breathers. So where is that oil coming through the breathers coming from? There is always going to be an oil mist flying around in the crankcase and rocker boxes. The higher the crankcase pressure the more of that oil mist is going to be blown through the breathers and into the intake system. Therefore crankcase pressure would seem to be the culprit.
Now let's think about how exhaust back pressure could affect crankcase pressure. For the exhaust pressure to find its way to the crankcase, the exhaust gases would need to travel through the valve guide/seal into the rocker box or through the piston rings and into the crankcase. Assuming either of those is happening, it only makes sense that increasing the exhaust back pressure would allow more exhaust pressure into the crankcase, and thus more oil mist through the breather into the intake system.
If you follow this train of thought, increasing the back pressure of the exhaust, if anything (and that's a big if - I don't think exhaust pressure, within reason, would have a significant effect on crankcase pressure provided the valves and piston rings are sealing properly), would increase the amount of oil in the intake system, not reduce it as you are proposing.
My thought process is simply that - my thoughts and opinion. I don't have any data or experience to back this up. You could say this is my theory, but it seems to make sense to me.
Does it make sense to you?
Think about it.
Oil in the air cleaner is coming from the crankcase breathers. So where is that oil coming through the breathers coming from? There is always going to be an oil mist flying around in the crankcase and rocker boxes. The higher the crankcase pressure the more of that oil mist is going to be blown through the breathers and into the intake system. Therefore crankcase pressure would seem to be the culprit.
Now let's think about how exhaust back pressure could affect crankcase pressure. For the exhaust pressure to find its way to the crankcase, the exhaust gases would need to travel through the valve guide/seal into the rocker box or through the piston rings and into the crankcase. Assuming either of those is happening, it only makes sense that increasing the exhaust back pressure would allow more exhaust pressure into the crankcase, and thus more oil mist through the breather into the intake system.
If you follow this train of thought, increasing the back pressure of the exhaust, if anything (and that's a big if - I don't think exhaust pressure, within reason, would have a significant effect on crankcase pressure provided the valves and piston rings are sealing properly), would increase the amount of oil in the intake system, not reduce it as you are proposing.
My thought process is simply that - my thoughts and opinion. I don't have any data or experience to back this up. You could say this is my theory, but it seems to make sense to me.
Does it make sense to you?
Outstanding HDF Member
Joined: Jan 2010
Posts: 2,916
Likes: 31
From: earth
Swing and miss with the backpressure hocus pocus. Two things come to mind, your pump is not scavenging properly or oil is not draining out of the heads properly. Since you already have Doherty Myst free breathers, check the oil return ports in heads for debris blockage and make sure they were opened up to the recommended .089 drill size. Also look to the oil pump for misalignment, damaged orings, damaged gear rotors, or damaged camplate.
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Tourer
Joined: Oct 2009
Posts: 407
Likes: 2
From: Bixby Oklahoma
Can't say I disagree about trying to increase back pressure causing more crankcase pressure. Its just a mystery to me why I am getting the amount of oil on the cam chest and why there isn't a fix for it. I drilled the back plate (the stand off where the hollow bolt is, for some brass fittings that run hoses to the ground (SE backplate) and plugged the small holes with set screws where the mist enters the throttle body from and still have no luck. As I said, pretty frustrated.
Last night since the AC filter is taller /wider than stock, I took an old football AC cover and cut a couple inch long strip out of the side and JB Welded it to the inside bottom of my currrent round (nostalgic I think) cover to extend under the filter seal in hopes of being able to hold a folded up paper towel to catch the drips. Taking a short trip tomorrow - couple hundred miles - so I will see how that works.
thanks again for anyones comments - still open for the real fix
Last night since the AC filter is taller /wider than stock, I took an old football AC cover and cut a couple inch long strip out of the side and JB Welded it to the inside bottom of my currrent round (nostalgic I think) cover to extend under the filter seal in hopes of being able to hold a folded up paper towel to catch the drips. Taking a short trip tomorrow - couple hundred miles - so I will see how that works.
thanks again for anyones comments - still open for the real fix
Thread Starter
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Tourer
Joined: Oct 2009
Posts: 407
Likes: 2
From: Bixby Oklahoma
I guess the oil pump might need changed to the Fueling if that is the problem because the shop assured me they aligned teh stocker correctly. I hadn't thought about the holes being clogged because they are bigger than the original but its worth a look.
Shop also recommended the oil pump change out - thats a lot of paper towels $$$
Shop also recommended the oil pump change out - thats a lot of paper towels $$$
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I made new crank case breathers for mine. No oil issue. I don't run my oil tip-top full either.
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