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Harley Oil Sumping Fix: Quick Solutions for a Smooth Ride

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Mr. Chase Manhattan

Oil sumping, a common issue for Harley-Davidson motorcycle owners, pertains to the undesirable accumulation of oil in the lower parts of the engine, specifically the crankcase. This problem can lead to reduced performance, and in some cases, could cause damage to your bike’s engine. Recognizing the signs of oil sumping is imperative for timely and effective intervention. You might notice symptoms such as unexplained oil leaks, a decrease in engine performance, or excessive oil presence in areas where it shouldn’t be.

Harley-Davidson is aware of the oil sumping issue, particularly in some models like the Milwaukee-Eight engines from years 2017 to 2019. The manufacturer has responded by redesigning the oil pump for its 2020 models, which serves as a key fix for the oil sumping dilemma. However, there are also other avenues you can explore, from preventative maintenance to aftermarket products, to ensure this issue doesn’t dampen your riding experience. Regular checks and maintenance could potentially save you time and money, while also extending the lifespan of your engine. But what else do you need to know?

Related read: Milwaukee 8 Oil Pump Recall: What You Need to Know Now

Oil sumping can seriously affect your motorcycle’s performance. It’s vital that you understand what it is and the common causes to effectively prevent or address this issue.

What Is Oil Sumping?

Oil sumping, sometimes referred to as wet sumping, is a condition in Harley-Davidson engines when excess oil accumulates in the crankcase rather than being properly circulated and returned to the oil tank. This can lead to a variety of problems, as the oil should be cooling and lubricating the engine. If it’s sitting in the crankcase, it’s not performing its necessary functions, which can result in engine damage and reduced performance.

Common Causes of Sumping

The causes of oil sumping in Harley-Davidson motorcycles typically relate to the oil pump’s performance. The oil pump is critical in maintaining proper oil flow and pressure throughout your engine. Here are some factors that might contribute to oil sumping:

  • Malfunctioning Oil Pump: A failing oil pump can’t circulate oil effectively, leading to accumulation in the crankcase.
  • Clogged Passages: If the oil pathways within the engine are clogged, oil can’t return to the oil tank, backing up into the crankcase.
  • Worn-out Components: Over time, engine parts like check valves wearing out can prevent oil from flowing as intended.

By addressing these issues, you can prevent the risk of oil sumping and ensure your motorcycle runs smoothly and reliably.

When your Harley starts behaving strangely, you may be dealing with oil sumping. This condition can affect your bike’s performance, and identifying it early can save you time and money.

Symptoms of a Sumping Harley

  • Power Loss: If you’ve noticed your Harley losing power, especially during acceleration, this could be a symptom. Sumping can starve your engine of the oil it needs, causing reduced performance.
  • Pressure and Leaks: Watch for unexplained drops in oil pressure or oil leaks beneath your bike. These could indicate that oil is not being properly recycled back into the system.

Diagnosing the Issue

  1. Visual Inspection: Check if there is excess oil collecting beneath your engine or in the air cleaner.
  2. Ride Test: Go for a ride to get your bike up to operating temperature; observe if performance issues arise during consistent RPM ranges.
  3. Oil Level Check: After running your bike, let it rest and then check the oil tank level. A higher than normal level can signify sumping as oil accumulates in the bottom end.

When your Harley experiences oil sumping, the solution involves a specific repair approach. A crucial element is selecting the appropriate repair kit, which typically includes a new oil pump, as well as gaskets and o-rings required for the repair.

Selecting the Right Repair Kit

To address the sumping issue effectively, you need a repair kit that is compatible with your Harley-Davidson model. For 2020 and newer models, the redesigned oil pump that comes stock is designed to resolve sumping. If you have an older model experiencing sumping, you may need to obtain this oil pump separately.

Your repair kit should include:

  • New oil pump designed for your specific Harley model
  • Gaskets to ensure a proper seal during installation
  • O-rings essential for preventing leaks

Ensure the kit is designed for your motorcycle’s specific engine type to avoid compatibility issues.

Step-by-Step Fix Guide

Follow these steps to fix the oil sumping problem on your Harley:

  1. Drain the Oil: Safely drain the engine oil and dispose of it according to local regulations.
  2. Remove Components: Depending on your Harley model, remove necessary components to access the oil pump. This may include parts like the exhaust system or certain covers.
  3. Extract Old Pump: Take out the defective oil pump, along with the old gaskets and o-rings.
  4. Prepare New Pump: Ready the new oil pump by attaching new gaskets and o-rings where required.
  5. Install New Pump: Carefully install the new oil pump in the exact place of the old one, ensuring everything aligns properly.
  6. Reassemble Bike: Put back all components removed during disassembly.
  7. Refill Oil: Top-up with fresh motorcycle engine oil to the recommended level.

It’s essential to follow your motorcycle manufacturer’s guide or a trusted repair manual during this process. If you’re not confident or experienced in performing such repairs, consider soliciting the help of a professional mechanic.


Proper maintenance of your Harley can prevent oil sumping and keep your ride smooth. It’s crucial to conduct regular inspections and consider timely upgrades, ensuring your motorcycle performs optimally.

Regular Checks and Balances

It’s important for you to regularly inspect your motorcycle’s engine oil level and quality. Make it a routine to check for any oil leaks or unusual signs of wear:

  • Engine Oil Inspection: Before any long ride, check the oil level through the inspection window or dipstick. The oil should be clean and at the recommended level.
  • Check Valve Examination: Ensure the oil check valve is functioning properly. This valve’s health is pivotal to preventing oil from flowing back and causing sumping.

Routine Replacement and Upgrades

Maintenance often involves replacing worn-out parts that could lead to larger issues like oil sumping:

  • Oil Pump Replacement: If your Harley is experiencing oil sumping, upgrading to the newer 2020 model oil pump can be a definitive fix.
  • Routine Maintenance:
    • Replace engine oil and filters according to your service manual’s intervals.
    • Keep an eye on service bulletins for any recommended upgrades that can improve the integrity of your motorcycle’s oil system.

When it comes to rectifying the oil sumping issue with your Harley, understanding the potential costs and selecting a reputable dealership for professional services are crucial steps.

Repair Costs Estimation

Parts: The primary part needed for the fix is the updated oil pump. Depending on your model, prices can vary, typically ranging from $150 to $300 for the part itself.

Labor: Dealerships charge labor by the hour. For this type of repair, you’re looking at approximately 1-3 hours, depending on the complexity of your specific model and labor rates, which can range from $80 to $120 per hour.

Your total estimated cost can be between $230 and $660, combining both parts and labor. Keep in mind, if your bike is still under warranty, you should check with your dealer as this might significantly reduce your repair costs.

In this section, you’ll find answers to common questions about oil sumping in Harley motorcycles, giving you a clearer understanding of what it is, how to address it, and the solutions available for your bike.

What are the common indications of oil sumping in Harley motorcycles?

Oil sumping, or wet sumping, is often indicated by reduced engine performance, excessive oil usage, and sometimes oil in places it shouldn’t be, like the air cleaner. If you notice these symptoms, it’s possible your Harley is experiencing sumping.

Which models are affected by the M8 oil pump issue, and when was it addressed?

Harley-Davidson models with the Milwaukee-Eight (M8) motor, specifically models before the 2020 updates, experienced oil sumping issues. Harley-Davidson addressed the problem by redesigning the oil pump starting with the 2020 models, which now come with the improved pump installed as standard.

What can be done to prevent wet sumping in Harley bikes?

Preventive measures include regular maintenance, ensuring proper oil levels, and using quality oil filters. Upgrading to the latest Harley-Davidson oil pump if your model is pre-2020 can also minimize the risk of sumping.

What causes oil sumping to occur in Harley engines?

Sumping can be caused by issues in the oil pump alignment or bad seals, which allow oil to accumulate in the engine crankcase, leading to lubrication and performance problems.

How effective are the sumping fix kits available for Harley motorcycles?

Various sumping fix kits, including upgraded pumps and seal kits, offer effective solutions. Installing a redesigned oil pump from the 2020 Harley models has proven to be a reliable remedy for the oil sumping issue.

Are there any long-term solutions for addressing oil sumping in Harley engines?

Installing the redesigned 2020 Harley oil pump, as well as staying on top of engine maintenance, are long-term solutions that have been effective in preventing sumping. Regularly consulting with a service manager for appropriate maintenance and updates can also help ensure long-term engine health.

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Hey y’all! It’s Chase Manhattan, a life-long gearhead, tinkerer, and adrenaline junky. I like to write about all things technical in the Harley Davidson and motorcycling space.