Oil Dripping from Harley Air Cleaner

Question Hi guys. I’ve been doing all of my basic maintenance on my 08 Electra Glide Classic thanks to your videos. I noticed today that I have some oil dripping from my Harley air cleaner housing onto the right side of the motor. It’s not much, but I’m concerned. No recent service to the bike except for a new battery a couple of weeks ago (I installed it). It hasn’t been dropped or on its side. The oil level is right where it should be on the dipstick when cold. I’ve done all the fluid changes and am very careful not to overfill. Any help would be appreciated.

Answer Top breathing engines breath, or vent, through the top breather bolts which are threaded into the heads of a Harley Davidson motor. The air inside a motor is saturated with oil. It exits through the breather bolts and into the air box where the air is filtered and the oil is captured in the air filter. A larger motor or a built motor will, typically, breath heavier. When oil drips out of an air cleaner assembly, it is usually an indication that the air cleaner element is due to be cleaned, or changed.

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More Info:
Here is an article we like from MotorcycleCruiser.com. It explains why you had oil pumping out if your air cleaner assembly. The only other reason for this to happen can be from a broken oil pump or overfilling, as you mentioned.

Understanding Blowby in Motorcycle Engines

If you ride your motorcycle too gently early on, you may never get the piston rings seated. Then Bad Things happen…like blowby and oil where it doesn’t belong. From the April 2005 issue of _ Motorcycle Cruiser _ magazine. Read on for the causes and every now and then I receive an e-mail from someone wondering why he’s suddenly finding large puddles of engine oil in his air filter. While some oil misting in the air filter is normal and nothing to worry about, these guys, who invariably own large-displacement, high-mileage V-twins, are talking about a regular Exxon-Valdez, enough to make a real mess and require topping off the oil supply on a regular basis. Because this is an area of general interest, let’s discuss what’s happening.

By nature, all four-stroke engines require ventilated crankcases. The reason is twofold. First, when an engine is started or run at low temperatures, condensation takes place and fuel vapors migrate into the crankcase. These contaminants, essentially water and raw gasoline, mix with the oil to form engine-damaging sludge. Fortunately, once the engine reaches operating temperature the water turns to steam and the fuel remnants percolate out of the oil. As long as the crankcase is vented, either by the atmosphere or by using a positive-pressure system, these nasty byproducts are free to drift out of the engine and go their merry way without causing any harm.

The second reason the crankcase needs a vent is because no matter how hard we try, there is no practical way to eliminate air from entering it. Anytime the engine isn’t running, atmospheric pressure pushes air into the engine through open valves or any other convenient entry point. When the engine is running, some combustion gases normally make their way past the rings to pressurize the crankcase as well. If the crankcase wasn’t vented, pressure buildup would soon cause every seal in the engine to rupture as the trapped air sought a way out.

Originally, crankcase vents were nothing more than tubes connected to valves timed to open when crankcase pressure was too high and close when crankcase pressure was too low. This allowed the bad stuff to be forced out and prevented dirt from being drawn back in. A variation on this scheme vented the crankcase through a series of baffles, accomplishing the same thing with less complication. Although they were efficient, these breather-tube ventilators were little more than open pipes spewing engine contaminants directly into the atmosphere. As you can imagine, the EPA took a dim view of the situation and demanded that manufacturers, first car and later motorcycle, do something about it.

Although system details vary, one solution was to plumb the breather into the air cleaner. The fumes coming from the crankcase are then recirculated back into the engine and burnt.

Here’s how the oil ends up in the air cleaner. Crankcases can only contain a given volume of air and its attendant pressure. Once that pressure is exceeded, you’ve got problems.

What causes excess crankcase pressure? Excellent question, grasshopper. For starters, anything that can reduce the crankcase volume, such as overfilling it with oil, creates problems, as will a restricted or damaged breather system. In V-twins, crankcase pressure sees rapid fluctuations, decreasing as the pistons rise in unison, then increasing sharply as they descend, compressing the gases in the crankcase. But the most common culprit is usually something called blowby.

Blowby occurs when the piston rings fail to do their job properly. They may be worn or they may never have seated properly in the first place. This failure to seath the rings tends to be somewhat common is large-displacement V-twins. That is partially because they make good power down at low rpm and small throttle openings. However, it takes large throttle openings and high rpm to get the rings seated. If you went through those first few hundred miles without ever holding the throttle open or revving to the power peak—or only did it once or twice—your rings probably never seated.

The bottom line is that the piston rings can no longer effectively seal the combustion chamber. Combustion gases are leaking past them, pressurizing the crankcase. This creates all kinds of problems; seals leak, gaskets fail and, because the pistons are forced to compress the excess air on the downstroke, horsepower is lost. But these things don’t happen right away.

Because the hot oil in the crankcase is easily displaced by the increased pressure and because it has a perfect path out of the crankcase via the breather, the first sign of impending trouble is nearly always oil migrating into the air filter.

Once the oil is pushed into the air cleaner, much of it condenses and drops out of the airstream, making a mess in the process. If this was the only problem it’d be bad enough. Unfortunately, some of the oil is pulled back into the engine along with the vapor and burnt, where it does more damage by glazing the cylinder walls and creating carbon deposits in the combustion chamber. At this stage the engine is on a downward spiral. It’s only a matter of time before you’ll be doing a top-end job.

I’d be remiss if I didn’t mention that some engine designs are more likely to experience top-end sealing problems and/or breathing issues than others. In particular, large-bore twins, V or otherwise, tend to push more oil than an equivalent-displacement multi. This is simply because dinner-plate-size pistons moving through sewer-pipe-dimension bores are more difficult to seal and move greater volumes of air. As a side note, there are also some bikes with poorly designed breather systems, but that’s a separate issue to be discussed another time.

Please don’t get the mistaken impression that all large twins are just ring-eating monsters waiting to self-destruct; they aren’t. Chances are the majority of us will never have a problem with blowby. But like they say, recognizing a problem is always the first step in curing it.

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127 Responses to “Oil Dripping from Harley Air Cleaner”
  1. Tom Swanson

    I have the same problem, and yes, my filter does need to be cleaned. I have an after-market spike filter. The breather bolts feed into a secondary filter to collect and filter the oil, but it has started dripping onto the bike recently. I’ll clean both filters and see if that fixes the problem.

  2. bengus60

    If its a k /n air filter it may be over saturated or over charged with oil if it was cleaned

  3. Shawn

    It’s likely you have too much oil in the crank, check your oil hot and have the level remain at the half way full mark or just slightly lower.

  4. Greg

    I have the same issue, a few months ago I changed the stock air cleaner to a K & N element. At the same time I removed the backing plate and painted it to match the denum paint! Put everything back together, minus the ugly football cover..I replaced that with a medallion which I love. Ever since than I have had dripping oil that as I go down the road gets all over the sattle bag, the oil is right at the correct level…very frustrating. I also cleaned the filter, and no change. What to do??

      • James Winterstein

        I had same problem on my 113CI motor. Installed “demysters” which solved the problem. The venting bolts do not do the job on bigger motors especially on longer sustained speed rides.

        • Marty Willis

          Thanks for all above…I just changed the battery (got stuck at the gas station)- then went out for test drive afterwards- and sure enough, the engine light came on- has to turn back- then I saw the oil stains on the cleaner bottom and bottom of the “V”…no oil elsewheres (line was good, etc.)…so I took off the cleaner, and yep, all in sode at the bottom, and at the ends of both breather tubes had a CL2 leak. With the cleaner off, I started the engine, revved it up to 3K and and idled, and the engine light went out…so….I hoping its “just” the cleaner. I have an ’07 Electra…I’ll let you know when I get ‘er changed- thanks all! Really, thanks!

  5. EMBRY


  6. Tyler

    I just upgraded my intake to a Screamin Eagle Stage 1 intake. I run the filter with just a medallion instead of the full cover. Knowing that my bike leaks a lot of oil, I had considered routing the breathers to a tube with a filter on the end, to the bottom or rear of the bike. I’ve read that cold dry air is better for the bike. Creates more power, and would reduce carbon buildup in the chamber and on the piston, but I’ve also been told that the oily mist also lubricates the top side of the piston. Which would you recommend. Rerouting or not?

      • Tyler

        I ride from Oceanside to San Diego and back 3 times a week, and my regular rides to work. Every 2 weeks I’m adding between half and a whole quart.

  7. Rodger

    If you will run with the oil at 1/2 quart low it will help. You still have plenty oil for the engine. As the oil heats up it will expand & can become over full. The oil is a normal Harley happening. I use a sanitary napkin (liner) in the lower portion of the air cleaner & change it out with each oil change. It keeps the oil off the engine.
    The only other option is to put an external breather kit on to keep the oil out of the air cleaner. This is a good idea also because it will help prevent carbon build up in the combustion chamber from oil deposits.

  8. Ramon

    Hip guys I also have the same problem I have a 2002 road king cvo 1550 with 90,000 miles and just recently I guest in the last 6 months started to drip oil from the air breather. It has a Rinehart exaust with and efi and a k & n air filter. My question is any ideas on what can I do to stop leak.

    • Customer Service Techs

      Hi, Ramon. The oil is residual from your engine breathing/venting. You can not prevent, or restrict this from happening.
      We suggest removing & cleaning your air cleaner element more frequently. Wash your K&N filter in warm, soapy water. Dish detergent works best. Then, blow it out with compressed air and let air dry.

      • Dave

        Same problem on a 2012 ultra.tried running low oil didn’t work just junk harley internal parts.

      • Adam

        Don’t blow out with compressed air! You will ruin the element. Shake the filter and them let it air dry.

        • Cheese

          Phooey… As long as it’s not high pressure, keep it to 10-15 psi, it’s fine. They also say not to use heat guns or blow dryers, but fine. On medium heat & high speed, it’s still way less heat & velocity than the element experiences during normal riding operations. A little 90-100 degree low pressureair (low enough to not compress the fibers, is perfectly fine. Hell, same exact media for diesel rigs, K&N replies you to use a pressure washer & compressed air.

        • Dean

          You can use compressed air, just don’t have the nozzle right up against the filter element

  9. Hwan

    If anyone can help me out I’d appreciate it! I have a 2000 Road King, just recently it started leaking oil out the air filter. I took it to the dealership and they told me my rocker seals were leaking, I had them replace it and also do a 40k service. Not 48 hrs later still did the same thing, took it back to the dealer and they than told me that an oil port in the head was clogged and the air filter housing was warped, so again had that all replaced/fixed. Another 48 hrs later still leaking, also it only leaks at highway speeds 70+ mph. Now it’s back at dealership and now they are telling me that the cam chain tensioner went and made the oil pump fail! Please help me!

    • Customer Service Techs

      Hi, Hwan. The dealership is approaching this the correct way. The reason they went into your rocker boxes was to replace your breather valves.
      If breather valves are bad, the motor may breath too heavily into the air cleaner assembly. At 40k miles, it is a logical thought that the breather valves may be blocked, or no longer functional. Next logical step would be going into your cam compartment to inspect your oil pump.
      Going by what you have told us; seems like they are on to your problem.

    • Tom

      Fire that money sucking dealer! He is ripping you OFF man! Just check the air filter regualtly keep it clean and run a little less than half full on the dipstick? How much did the dealer scam you out of? Please post this POS dealer so we can all stay away

  10. Bradford

    I have a 2002 Road King with an Arlen Ness big sucker air kit. After every ride I need to remove the air filter and wipe down the inside of the throttle body as well as the standing oil on the air filter element. I cleaned the filter as per the Arlen Ness directions but the problem still exists. I run the oil level about 1/2 down the stick as recommended. I have had a machinist friend of mine make new breather bolts for the air cleaner with venting out the top of the bolt to a fitting that will have a stainless steel hose venting under the bike. My question is can I block off the existing venting to the air cleaner so that now blow by gets to the air cleaner/throttle body. Will this affect engine performance or wear? does the engine need the vaccuum produced by the opening of the throttle body to work properly? Brad

    • Customer Service Techs

      Routing you breather line(s) beneath your motorcycle is fine. Just make sure that the engine’s breathing/venting is not restricted in any way.
      You do not need to have your engine breathing into your throttle body/carburetor. It is only that way for environmental reasons.

  11. Eric

    I was thinking of installing Vance & Hines VO2 Naked Air Cleaner, the breather tubes are directed back through the throttle body is that better than a breather kit? My concern of the kit is the routing of the drip hose so that oil isn’t dripping on the rear tire.

  12. Mike

    My 95 Evo was leaking from what I thought was the rocker boxes. It actually leaked for a year before I found the real problem.
    I always thought it was the front rocker box leaking and changed gaskets twice myself and had harley change once to find the same problem after hundreds of dollars. I went on fix it sites and no one mentioned that your lower frontlegs where they are put together with a seal and retainer ring can leak and spray a fine mist from the front tire and always looks like the front box is leaking. I noticed a very fine mist on my front fender but I thought it was from the box shooting oil,
    One day I decided to look into stiffening the front tubes so I pulled the front end apart and low and behold the seals where leaking. It cost me $100.00 and not one leak after a month!

  13. Matt

    I have a 1999 1200XLC. I am having a lot of oil dumping into my air cleaner. air filter replaced and even removed filter and still dumping oil. any ideas?

  14. EDWARD

    I have a 99 fatboy and made the mistake of letting someone change my oil. Gift card for a service. Anyway they over filled my oil and they filled it to the top I put about 30-40 miles on it and it stald on me. I noticed oil coming from air filter. I cleaned my K&N filter and changed the plugs. Still does not start, any suggestions on what to check or do. I am going to do a compression test next.

  15. Edward

    Had blow back oil was overfill when oil change was done. I put about 30-35 miles on it and it stald on me had blow back. So I cleaned air filter(K&N) and changed plugs. Bike still will not start. HD Fatboy 99′

  16. troy

    I picked up a 98 road king i was told in 2010 the evo engine was replace with the same crate size 80 ci evo my problem is it leaks oil out the front breather vent i took rocker box off the mushroom oil deflector was in the wrong place i put a new one in the rite place put back together same leak so i took off cam cover the breather gear was broke i replaced it put back together still leak, when i say leak i mean after 1/2 minute to 1 minute it will start leaking and wont stop till i shut it off then drains for a little bit more

  17. Billy

    I have a 2011 FLTRU and recently upgrade with true duals, free flowing breather/ filter and a download to tune the bike up. I typically run my oil a little low to help prevent the oil from dripping out the breather. And it still has some excess dripping. I was told by the local bike shop not to worry about that with all the air flow I have going through the motor that is normal. I haven’t had to add oil between oil changes. It’s just messy and and smelling oil makes me think I have other issues. I am looking for another opinion. Thanks

  18. Daniel

    I have a 2000 Heritage that has been upgraded with a Mikuni carb. I thought it was leaking oil from air cleaner but i just installed a new k&n and come to find out its gas leaking from air cleaner. I thought of the float but it does it only while riding and not all of the time. Help please

    • Customer Service Techs

      It may be leaking from the accelerator pump. Inspect the carb while you twist the throttle a few times. See if you notice any gas.
      Verify that your float height is correct and don’t forget to inspect your fuel lines & fittings.
      http://www.fixmyhog.com/posts/harley-tips/ (ZD: 3824)

  19. heinrpa

    Ok, I am experiencing the same exact problem with my 2009 Ultra. I have changed the air filter but the oil continues to seep out in small quantities. Any other suggestions? Could it be related to a stage one or two upgrade. Thank you.

  20. Bill

    I have a 1990 FLHTP with a 2000 rebuilt 1340. Its blowing oil Thur the vent tube. Any ideals?

  21. Jeff Parks

    I have a 2012 Streetglide with a 103 the only thing added from stock is a set of Vance&Hines Hi-out put slip ins I purchased a breather from a newer 103 the scoop looking one it looks like it will take in more air will this require it to be re mapped.

  22. Erik

    I’m experiencing a similar problem ten fold. I ride a 01 Electra with a twin 88 with a SE rebreather. We were on our way back from a 3 hr ride going 75 on a 95 degree day. Oil started pouring out of my air filter and blown down the bike. Trying to figure out what the deal is. I’m thinking possibly rings are shot or something in the rebreather system. Any thoughts?

  23. Robert

    I recently changed the screen in my tank for my 02 Dyna. After putting it all back together my bike started running rough and now a gas oil mix is pouring out of the breather tube above the carb. I recently had the tank painted due to a fender bender when I pulled the old screen there were paint chips on the screen. What could cause a major flow of gas oil mix to be pouring out of the breather tube and making the bike run and smoke horribly

  24. Mike

    I was told a long time ago that when that happened i.e. Was time for an oil change. Is that not true or was someone pulling my leg?

  25. Frank

    I have a ’92 LowRider with low mileage and a similar problem. If I take it out for a spin every week or two there’s no problem. But, if I let it sit for a month or so, the breather tube that plugs into the air cleaner spits oil into the air cleaner. If I unplug the breather tube and look, oil is spiting out (as if the pump is partially pumping). It continues for a few minutes and then stops (maybe a pint or so of oil total).

    I’d appreciate hearing your thoughts.


    • Customer Service

      We would be happy to assist you; we just need some more information. What is the make/model/year of your motorcycle?

  26. David

    I have a 2016 wide glide. I purchased it 5 months ago and it’s leaking oil in the same fashion. So I took it to the dealership and they gave me a new filter. I rode it respectfully for 500 miles over the next 2 months and it’s leaking again. I love Harley’s but this is rediculous. I shouldn’t have to be cleaning oil out of an air filter every few months on a brand new bike. Perhaps Harley Davidson should reengineer this part of the bike. Sometimes I think maybe it’s a conspiracy to get us to spend more money on an already outrageously priced machine. BUT. I love my bike!

  27. Nicholas ventura

    I have 2015 harleydavidson I have replaced air cleaner notice breather bolts has lot oil comes out on the filter I have a joker air filter what causes this thanks

  28. Greg

    whats up fellas, I just got my first bike, what I thought was a steal, its a 95 FXSTS 1340 ,according to the odometer it has 10K miles on it… I was told it had a larger cam installed at some point, has a “butterfly” style air cleaner on it, I could see the filter which looked dirty, I opened it up and noticed oil laying inside the filter housing, and the filter appears to have oil in/on it…ive read some of the post on here and it seems to be somewhat common, but a lot of the posts I have seen are newer bikes so I was just curious about my bike

  29. tim

    i have a 1991 ultra glide can you tell me if the air cleaner mounting bolts are hollow for venting or are they solid?

    • Customer Service

      The stock motor for your year and model is a bottom breathing motor.
      The bolts you are referring to should be standard / regulator bolts. Not breather bolts.

  30. Sandy

    I have a 06 Heritage classic which from day one had a S & S air cleaner installed. Problem has been excessive oil dripping out the air cleaner onto the cam cover. Local shop says and I quote “just put the stock air cleaner back on, it’s because your S & S is open backed. Hmmmm no one else with open backed air cleaner covers has this problem. Your thoughts please

  31. rodger fled

    i have a HD 91 ultra classic, evo engine, when it sits for a month, and I start it up. it blows oil out of the oil breather.. any idea why ? what can be done to fix it. thanks in advance .

  32. Roy

    My sportster forty eight is having issues finding neutral while running… Also noticed some oil leaking by the intake???

  33. Chris

    Hey guys, I am changing oil in 2013 Road Glide and noticed a threaded hole on the bottom of the cam case. Like 3/8″ back from the cover. There is no bolt in the hole. And a lot of oil around this area. Is there supposed to be a bolt /machine screw in this hole?

  34. Dylan

    I have a 2003 hd night train with the 88 motor. It is carbed. My bike was just serviced a month ago but yesterday I noticed oil coming from the air filter. By the end of the day I had no oil and my check engine light came on. I checked the codes and they’re all clear. It’s almost like the oil and gas are mixing and causing it to flood. Any idea what could cause this? Also I have a hyper charger air filter on the bike.

  35. Mack

    I have a 2005 Fatboy (w/95 inch kit installed) with about 48,000 miles on it.
    I was out for a ride last summer and oil started flowing out of my air intake.
    I have had one dealership tell me I need a new engine.
    I had another tell me I need new piston rings.
    And I had one tell me I need a new oil pump.
    Mind you none of them took it in and diagnosed it.
    The bike was still on the trailer when they told me.
    How do I figure this out.
    I had a friend tell me to check the plugs, if they are oily then it’s the piston rings.
    If they are clean its probably the oil pump.
    any suggestions.

  36. 11triglide

    my trunk lock broke and fell into trunk and i’m trying to open it any help would appreciated

  37. Brian

    ok so i have a 99 fatboy 1340 evo 44,000 just got it seems to run like a beast previous owner said he rebuilt the top end ok well prob im havin is smoking ive checked and cleaned my tappet found a tiny bit of metal . went on a 700 mile run recentlly and she started smoking could oit b my spring in my oil pump or is it my valve guide seals. the oil is not over filled. even running open no filter or anything carb ajustment?

    • Customer Service

      Hi Brian. If your motor is smoking, oil is getting by your valve seals – piston rings, or both.
      You will not be able to determine which until you disassemble top end.
      You will be addressing both at that point, regardless.
      You should not have any metal in your tappet screen.

  38. Con

    I just installed a new air filter, for the first time since I bought my bike last August. The bike only has 4000 miles on it, and the air cleaner was more dirty than I expected. It also had some oil on the back of the filter, and not being very mechanical, I wondered if I was disposed to put some oil in or on the new filter, (like a lawnmower)? I know that sounds pretty dumb, but I haven’t had a bike in over 25 years. So even though I’m pretty old, 64, and disabled, so I cannot hold up an 800+lb bike any longer. That’ why I went to a trike. I’m also new, to newer motors…

  39. scott

    Breather baffles in rockers may need changed out if oilin up quick after cleaning

  40. Wade Carden

    My 2017 FLHX is having a blowby problem from the air cleaner. Is this common on the milwaukee 8 and is there a fix?

  41. Isaiah

    Hey guys I’m stumped I got an 01 soft tail classic. I have oil spraying from my air filter. I changed the oil 3 weeks ago about 1000 miles and it ran great until this morning. Oil was filled and checked while hot. I have a k&n air filter and just replaced it, I tried to run my bike with the oil level at the bottom add line and it still dumped 1/2 a quart on a 30 mile ride home from work. All my hoses are clear and the oil is diffinatly coming from the rear breather tube. I’m thinking about replacing my breather assembly on my rocker arm assembly but was wondering if that was a good way to go. Any help would be appreciated

  42. kyle bingrn

    I have a 1991 Harley Davidson ultra classic. When the bike gets to normal operating temperatures it shots oil from the crankcase tube thru the carb. When first notices the whole side of the bike was covered with oil. It is not a mist, with air cleaner off it will shot 2feet from the bike till shut bike off. Do you think this is a bad check valve or do you think it is something else. Thank you for any help

  43. Kevin

    My air filter has less than 1200 miles on. Installed a new one on last oil change. Noticed some leakage today. 12/6/17

  44. Trigger Garcia

    I’ve got a 2006 Harley Softail Deluxe. It had never drip oil ever. Then two weeks ago I rode about 80 miles though what was basically a sandstorm with wind about 50 miles per hour, kicking up sand and tumbleweed and all sorts of crap. On my way home the following day, it was a calm day with zero wind. After about 40 miles the oil light began flickering.
    I pull over to a gas station. I noticed I was way way low on oil. In fact, it was undetectable. Since the gas station had no motorcycle oil the dealership I called told be that in an emergency I could you diesel oil until I got home then change oil.
    So I added two quarts of diesel oil. I rode about a quarter mile when I notice a steady flow of oil was pouring out from the air cleaner. I turn my harley off and then trailer it home.
    I am the least mechanically inclined harley owner you’ll ever meet. Any ideas what the problem might be?

  45. Callum Ayers

    Hey guys, looking for some help here.

    I have a 2003 Sportster XL Custom which has been running great up until a week ago when it started showing lean symptoms. I replaced my carburetor seal to the intake manifold and it seemed to run much better. Ran great for a week and then it started bogging out, hesitating and I figured it was the same issue (maybe the intake manifold seals that connect to the engine cylinders) but when I went to take my air filter off I noticed a squirt of oil had come out of the breather bolt which has not happened in the past. During this whole process I DID have my oil tank overfilled unfortunately, to the top line on the dip stick ( my buddy told me that it didnt matter if it was overfilled and Im a rookie.. now i realize it does matter)

    I am wondering if by overfilling my oil tank, I have over pressurized my crank case and fucked all my seals. Bike will not start now unless fully choked and even then it idles too high and bogs out. Pretty bummed and would appreciate any advice.

  46. Dennis Santopietro

    Q: I just built a 05′ CVO Ultra Classic,
    Bottom end done by Dark Horse, S&S Gear drives, T-3 cam plate and oil pump, S&S .585 cams, 10.25:1 dome top pistons
    .010 on the cylinders, heads completely reworked.
    The problem I’m having is a lot of oil blow by from the head breather vents, so much so I had to put a catch can to catch
    the oil so it doesn’t go all over.
    Last week the bike owner rode the bike approx. 200 miles with so much oil blow by it filled the catch can (approx. 2 cups)
    and then blew out the can over flow! Oil has never been overfilled in fact maybe a little under!
    Any Thoughts!

    A: That is blow by.
    Would suggest plumbing the top breather to the ground. Away from the rear wheel. Otherwise, you will have to get back into this motor in order to diagnose & correct.

  47. Franz Harker

    On blow by article. Had 28k on 08 ultra stock 96ci. Rings stuck to pistons ruined cylinders. Never had any oil loss in 5k miles not even an aircleaner wet. Under warranty they bored cylinders, new pistons and rings, but never relapped valves or new seals in heads. Ever since rebuild if i run at 3000 rpm on interstate for long rides i smell oil burning and oil at bottom of aircleaner. Have complained to dealer they say normal and harley wouldnt authorize head work cause not enough miles and not damaged. Come even a good car mechanic would have replaced the seals on the valves. I do, seals are cheap and not that labor intense. Any ideas or did i get screwed by the Big Corp. and end up with an oil sucker in 1500 miles / 1 qt. On interstate 75-80mph and 1qt / 3000 2200 – 2500 rpm highway at 60mph. Ideas?

  48. Brett Nagel

    Same problem on my ’17 Ultra Classic. (2,500 miles) 1/2 quart of oil gone between 1,000 mile oil change and 2,500 miles. Dealership broke it down found front cylinder scoring and rear cylinder valve seals leaking. Between the score marks he could still see the cross hatching from the factory boring. Technician said he’d never seen anything like it. Waiting on parts now, missing my girl.

  49. rick debny

    If you have a newer bike the umbrellas in the head need to be replaced.They control the breathing of the crankcase.It’s not going to be the breather element or the rings.I’ve replaced these twice in my own bike in the last 15 years.It is a bad design because all the rules for poulution.I redesigned the ports coming out of the heads eventually,I’ll try to attach a pic to give you the idea I did

  50. Aj Brackins

    Ticket 18342 My 2013 Street Glide is dripping oil from the breather. I have the cleaned the breather. I let the bike run just for a little bit to see if it was still leaking. On the back plate I have to holes that oil is still leaking from. Is that normal or not.

    • Customer Service

      Dear Aj,

      Thank you for your patience. In regards to your question-

      Some motors will breath heavier than others. Make sure that your air cleaner assembly is installed correctly and that the air cleaner element is clean.
      Suggest a K&N element of you do not already have.

      We’d love to have you be a part of our community. We are convinced you will enjoy the benefits of becoming a member and having access to the best instructional how to videos and professional tips. We would like to offer you a special promotion for your first-year membership.



      Fix My Hog Video Membership

  51. David Bird

    Regarding 1989 electraglide. Owing to personal circumstance my hog has being idle for quite a time. There is spark at plugs but oil spurting into air cleaner, and almost peeing out. When cranking. Battery is new so will turn over but not fire up. What is the issue and how to fix please

  52. dan kanyuh

    my 13 road glide blows oil out air cleaner.engine rebuilt to 117-120.is it just to much compression.or could rocker box vents be installed wrong.

  53. Brian

    GREAT write up! I have a question about my Shovelhead.

    1979 Electra Glide FLH 1200 King of the Highway full dresser.

    First off, NO she does NOT leak! She doesn’t “mark her spot”. I hate that.

    I found her December 2017. Sitting in a little Independent bike shop for sale. Previous owner had her 27-years.

    Lately I’ve noticed a very light mist of oil on the front face of the chrome battery cover. I’ve checked and tightened everything. Tappet blocks, all oil lines, rocker boxes, everything! The bike starts, idles and runs VERY
    well and is a blast to ride!

    In 2002 the previous owner upgraded the engine and transmission with all new bearings. The 4-speed is solid. All OEM with 3.00 first gear and shifts perfect.

    The 74″ FLH 1200 engine received +0.020″ forged pistons, S&S Super Stock
    single plug heads, Super E carburator, Head Quarters Torquer cam @ 0.465″
    lift, Jim’s Powerglide Tappets & pushrods, Alto clutch, true dual exhaust.

    All I had to do was new tires. Mounted Metzler ME888 Ultra Marathon Wide White Walls. The spoke rims are true straight.

    The Super E carburator runs a”dry” filter and in new this riding season.

    For the life of me I cannot figure out WHERE this oil mist is coming from!

    Thanks. Keep up the good work!


    • Brian

      I think I might have found it. Just for grins I ran a finger around the
      inner side of the S&S Teardrop air cleaner cover and found a
      small amount of oil. Removed and cleaned. OK for now.

  54. Frederick Thielsen

    I have a 1989 soft tail, I also have oil POURING out of my crank case venting filter, what’s up with that?

    • Customer Service


      You can try removing the oil pump check valve ball & spring.
      Clean the bearing and the oil pump bore, then stretch the spring about 1/4″ longer.
      Use a drag link or a chisel to unscrew the cap of the taller tower on the oil pump to access.
      If the bike continues to sump, you will likely need to replace your oil pump.


      Fix My Hog

  55. Jerry

    I solved the problem of oil dripping through oil filter, took off rocker covers and removed umbrella valve then drill out oil return hole, dont remember the size drill use, but it can be found online, then I put in new umbrella valve, I also got a drag specially bango bolt kit with bolts for the breather holes in the head, it came with tubing and a filter, installed the kit, then I modified the backing plate so no lines going to filter and ran both breather tubes to supplied filter, wa la no more oil going back to engine, the hell with EPA, putting oil back to the intake is bad creates carbon build up on your pistons

  56. Steve Walker

    I recently experienced this problem on my 2018 Street Glide. I. recently performed the stage 1 upgrades