Oil Breather

Discussion in 'Engine, Fuel and Exhaust' started by jwquinn, Jan 9, 2014.

  1. jwquinn

    jwquinn Member

    Hey everyone! So I'm starting my big cam and push rod project this weekend, and of course there's a bunch of stuff that has to come off before I open the cam chest and cut out the push rods. I have a SE Stage one air cleaner installed. When I pulled off the filter, there was - what I thought at least - quite a bit of oil at the base of the filter back plate. Enough so that I could push my finger through it. The throttle body butterfly valve was caked in oil and a bit of dust. I was able to clean it up with a rag easily enough. It wasn't horribly thick, but it was more than I expected.

    The only place the oil could have come from was the two breathers, and when I pulled those out, the tubes were wet with oil. Again, it didn't seem awful, and I know that there's oil in the gasses that are passed through the breather. I'm worried that I might be fouling my intake valves. I run Seafoam through the fuel system at every oil change. I haven't noticed any smoke coming from the exhausts.

    Does anyone have any thoughts on how much oil is too much inside the air cleaner? I was thinking I might have overfilled the oil tank last oil change, but it didn't seem so at the time. I appreciate any thoughts and insight - thanks! Oh, and I'm riding a 2012 FLSTC. :rider
  2. Bodeen

    Bodeen Well-Known Member Staff Member Moderator Contributor

    Many have found that running the oil level a bit lower than full will help with this issue. You are correct in thinking that carbon build up due to the oil burning can be as issue. Try running your oil level a little lower and see what happens.
  3. dolt

    dolt Senior Member

    Over filling will usually result in more oil than you are seeing but will definitely contribute to the problem. I have never subscribed to the theory that one should run the oil level lower than what the manufacturer recommends.

    Vent the heads to the ground or catch can. You are dumping that oil mist back into your throttle body and into the combustion chamber and burned off. When you turn the bike off the oil mist sits in the cylinders; the mixture is acidic and will eat the walls and the top ring. If you ride every day, this is less an issue but the remaining issue is the carbon buildup on the pistons as the oil mist burns off.

    The later models have the stamped, and supposedly more effective, head breathers so that element is OK. The first thing I would do would be to pull the rocker supports, very simple and straight forward job, and drill the drain hole under the brearthers to 1/8" or even 5/16".

    The next thing I would do would be to vent the breathers to the atmosphere or to a catch can. There are many ways to do this. Some guys go so far as to use braided hose and aluminum fittings to dress up the venting; looks very "aircraft". Being thd "dolt" that I am, I fabricate a cathc can from a piece of PVC pipe, end caps and plastic fittings to connect the hoses. Depending on the air filter backing plate that you have, you may have to drill and tap the plate to install barbed fittings to connect hoses from the breathers to the catch can, or whereever you plan to vent them. You would also need to block the backing plate openings where the OEM breathers connect; different ways to do this as well. The below photo is of poor quality but I think you can see the catch can hanging behind the air cleaner. There is hose that you cannot see venting from the top of the catch can between the cylinder V and down between the inner primary opening. That hose is zip tied to the frame below with a small lawn mower fuel filter attached to the end of the hose. The catch can is filled with the mesh that is inside the OEM breathers to catch most of the "wet" stuff and the fumes vent out the top of the catch can to the lawn mower fuel filter which catches most of any remaining "wet" stuff so there are no drips on the garage floor; well I do see one after a long hard ride. The catch can has a drain valve that I open occassinally to drain and trapped "wet" stuff but very little comes out, which means my ring seal is pretty tight.

    If there is any interest, I can post several photos of the way others have addressed this issue. The below photos show how I have addressed the issue on my bikes but there are lots of options.

    Doherty vented catch can. Works well but once the mesh media inside the can becomes saturated, the oil mist will drip onto the motor case. Not a big deal; teh can halves "thread" together so just open up and replace the media.

    Prepping the SE backing plate for vent hoses.

    The PVC setup on my '02 FLHT
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