Head breather tube

Discussion in 'FXR Models' started by grw58, Jan 20, 2013.

  1. grw58

    grw58 New Member

    Running a 87 FXRS with Screaming Eagle Heads. Was having problems with oil in air filter. Upon inspection noticed prior owner removed the head breather tube and replaced it with solid bolts. Had crank vented into back of air cleaner. Is this acceptable, or is there going to be to much pressure in the motor ? I think I have the right part on hand, are the head vent holes all standard on Evos or are there different sizes?
  2. fin_676

    fin_676 Experienced Member Staff Member Moderator Contributor

    Head Breathers were introduced as standard in the 1993 model year prior to that crankcase breather was directly from the crankcase and was vented into the rear of the air cleaner box
    My 02 softail has the breather heads but solid bolts and is vented from the crankcase
    it may be that you have excessive pressure in the crankcase forcing oil up out of the breather this issue can be caused by cylinder pressure getting past the piston rings
    A compression test may be a good idea at this point

  3. Breeze3at

    Breeze3at Well-Known Member

    Pre head breather bolts were 5/16" and head breather were 3/8" (I think).
    Your FXR has the oil tank under the seat doesn't it? Many Evo oil pumps allow oil to seep past the check valve (sumping) after sitting a while, and it pukes out when started. In addition to the comp. check Fin suggested, you may want to check if this is what is happening. Also you can just run the vent tube to the ground or a catch can instead of to the carb.
    oldironheads likes this.
  4. Jack Klarich

    Jack Klarich Expert Member

    If you have the time, a manual and some wrenching ability you could pull the cam cover off and check or replace your breather and see the self help section for re seating your oil pump check valve
  5. TQuentin1

    TQuentin1 Well-Known Member Staff Member Moderator

    My '91 Dyna is vented as you describe.

    I think Jack is on track here along with Brian's suggestion that you check the compression. A bleed-down test would be helpful along with a dynamic compression test.

    Is there any history that the cam chest has been opened up? Is there any possibility that the breather gear has been installed incorrectly?

  6. Jack Klarich

    Jack Klarich Expert Member

    Just a heads up on the breather, Harley made alot of mistakes here 1 being they used a plastic breather that scored the cam chest pretty bad, IMO I would have a look at this and replace and check the end play. You can modify the breather screen for better oil scavenging = less oil mist in the air cleaner:s
  7. flst89

    flst89 Member

    Your bike originally came with the breather hose connected to the carburetor backing plate.

    In theory , any oil from the breather would go into the intake and be burned by the engine. In actual practice, it seemed like most of this excess oil would be all over the side of the bike, or all over the passenger.

    Many of us have relocated the breather hose so that it runs down on the frame, outboard of the rear wheel.

    If your oil level is correct, and your engine and oil pump are healthy, you should get very little oil from the breather.

    Here`s a pic of where I ran the breather hose and transmission vent hose on my `89 Softail.

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