Oil Sumping ’92 Heritage

Question While starting up the bike this week after winter storage, I noticed oil pouring out of the oil breather and had to shut it off. What could be the problem?

Answer Hello Larry,This problem is known as oil sumping, it happens when then gravity and static pressure of oil in the tank located above the oil pump push the check ball upward and oil drips into the crankcase. Below the flywheels locate the breather hose and put it into a 2 liter soda bottle. Start the m/c and let it pump itself out approx. 1 to 1 ½ qts depending on how long the m/c sat and sumped. If you use a clean bottle, you can put the oil back into the tank. Make sure sumping has stopped out of the breather hose and cap off oil system when m/c has warmed up. Do not add more oil until sumped oil has stopped coming out of the breather hose or oil tank will be overfull and blow dipstick out of the tank and make a mess. There is no good reliable repair for this problem. Use the bottle on your breather hose at first start up, it may not do it every year depends on where the engine stops and how long it sits. Also yours is the last year of that style oil pump and breather system.
Wrench Safe, FMH

QuestionI need some HELP. Recently bought a 1990 softtail and tried to start it after its been storage for 4-6 years. as the engine cranks over and fires there’s a stream of oil coming from the hole in the round plate that the air filter is attached to. what’s causing this and how do I fix it/ there is an oil line coming from the back of the oil pump that goes directly to this location.
Thanks, Max Hall

Answer Hi, Max. While your bike sat, oil sumped to the bottom of the crank case; it now needs to be evacuated. You have a bottom breathing motor and it “breathes”, or vents, through the oil line that is routed to your air cleaner assembly. The excess oil will exit from this, bottom breathing, vent line. Remove the oil line from the back of your air cleaner backing plate. Make an extension, so you can run this line downward and into an oil drain pan or container. Verify that you have enough oil in your oil tank and let this m/c run for a little while. This will evacuate the rest of the lingering, old, oil. After this is resolved, be sure to change your oil & filter.

Question 1988 Harley Davidson FLHS – My Name is Michael. I own a MC repair shop in Oak Harbor Wa. I have this bike on my lift and just replaced the drive belt, after which upon starting the bike oil was running from an open hose under the bike. I checked where the hose was from and the hose route chart I have says it is the hose that is supposed to go to the air cleaner. This bike has a S&S G carb on it and matching air filter with no breather attached. I decided to run an independent breather and mount it higher than the engine….still there is oil blowing out of it…..HELP….it does not have breathing heads….why is oil blowing out of this hose?…can you help me!

Answer That is a bottom breathing motor. The open oil line is your bottom breather. It was originally plumed to your air cleaner assembly when everything was stock. The S&S backing plate has an allocation for a 90 degree fitting where the line can be routed, however it is typically better to route the breather hose to the ground (EPA would disagree).
Oil has sumped into the bottom of your crankcase and is blowing out of the breather line. This is typical after a bottom breathing bike sits for a prolonged period of time. If the bike has not been sitting and this is happening, we would suggest inspecting your oil pump. Open the inner tower to inspect for any foreign debris that may keep the check ball (bearing) from seating. You can stretch the spring 1/4″ longer as well. If the problem continues, you will need to inspect your oil pump gears & breather valve.

Question I’ve seen on your Fix My Hog webpage mention of “Sumping” which causes loss of power. Is there a test for this and what is usually involved correcting the condition? In terms of hours of labor at a dealer, what would you expect it would take to fix it?

Answer Sumping does not cause loss of power.
It is when engine oil seeps/sumps into the bottom of the motor’s crankcase. Upon start up, the oil eventually returns to the oil tank. On older, bottom breathing motors (pre 96) sumped oil would also pump out of the bottom breathing vent and onto the ground. Softail models and older FX models are more likely to sump because of the high oil tank location. Gravity comes more into play. Touring models have an oil pan, in a low position, beneath the transmission.

Question 1988 XL H 883 I recently got this bike a couple weeks ago. It been sitting in a garage for quite sometime. I got the bike running. I would start it everyday and take it around the neighborhood to keep it running until tags came in. Well, I started this bike yesterday and it was running for about 30sec and the oil dipstick popped off the oil tank and oil was over flowing out of the tank. Never seen this before. Any chance you could help me where to start?

Answer Your oil was, most likely, over full. If the bike sat for an extended period of time, oil may have sumped into the crankcase. Sometimes, the oil tank may actually look completely empty after sumping. If anyone added oil at that time, it was over filled. You may not have previously run the bike long enough for it to scavenge the oil in the bottom of the crankcase: enough to have the fill plug pop out. Suggest setting the correct oil level with the bike standing upright.

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13 Responses to “Oil Sumping ’92 Heritage”
  1. Allen

    Will a stronger spring fix this or mess up oil pressure in any way? Im installing a miniature oil pump electric 12vdc to the breather hose under bike and returning oil to tank at new fitting or to return oil line with 1 way check valve! How about that for a fix and only about 25.00 for parts.

    • Customer Service
      Customer Service

      Hi, Allen. Often, stretching the spring about 1/4″ (longer) helps. Make sure the oil pump bore is clean and the check ball is not pitted in any way. Would not recommend adding a pump in line with your return line. In fact, you really don’t want to be pumping ANYTHING out of there. It should only be breathing through that fitting. If you have excessive oil sumping, you have to diagnose why. Not help oil to better flow. http://www.fixmyhog.com/posts/harley-tips/

  2. Dennis Santopietro
    Dennis Santopietro

    Q: 1981 FXE. Every now and then when I start the bike oil comes out of the crankcase breather tube maybe about a 1/2 quart. Plenty of oil pressure I don’t suspect the oil pump. Can you tell me what I can do for this.

    A: You can use an 11/16″ drag link to remove the plug near the rear tappet block in the crank case. Clean the screen & check ball. You can stretch the spring 1/4″ longer. It may help. Problem persists or ever gets worse, replace oil pump with S&S pump.

  3. John

    Ticket 20085 I am having major problem with my Twin Cam 2003, my oil tank was 1/2 Oil & 1/2 petrol – why I have no idea from one day to another. Now I have drained the damaged oil, fill in with new oil to flash the engine. Removed the CV carburetor and want to order the MIKUNI 42- 18 HR42 EASY KIT – can you advise me what to do? Thank you in anticipation.

  4. Mike

    What causes a steel breather gear on a 91 evo to work it’s way into the case and become completly stuck won’t move in any way

  5. Walter

    Do you have information on the SUMPING that is taking place on the new Milwaukee 8`s? Is it pertinent to a particulate size engine or ALL of them?

  6. patrick long
    patrick long

    Hi folks,
    I have 93 FX/softail with a S&S sidewinder kit, I just had it sitting for a few weeks while i added a jagg oil cooler and repaired a leaking leaaking gasket. When i removed the rocker box i found two umbrella valves , one on each side, Would there be any reason for that? I just went off the manual and installed one closest to the air breather. I also gave her plugs and new filter. When I ran it about 1/4 mile and she started to blow oil out of the filter, a fair amount. I stopped it right away. Is this just build up in the crank from sitting a few weeks ?
    Also has the S&S carb with new K&N filter.

  7. KIM

    do i have to separate the motor from the trans to replace the oil pump on a 97 evo not enough room to get bolts or shaft out ?

    • Customer Service
      Customer Service

      Hello Kim,

      Thank you for your patience while I asked the experts, here is the reply:

      No. You should not have to get involved doing anything like that.
      You can remove or install an Evolution oil pump a few different ways.
      You may need to remove your outer oil pump cover 1st. Then, remove the retaining ring from the oil pump shaft. Remove the outer gears, then remove the oil pump body and inner gears. Finally, remove the retaining ring on the opposite side of the oil pump shaft (inside the cam compartment) and the oil pump drive gear. At this point, the oil pump shaft can be removed if it is not to be reused.


      Wrench Safe,

      Fix My Hog