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Harley Oil Sumping Fix: A Comprehensive Repair Guide

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Harley oil sumping is a common issue that many Harley-Davidson owners face. It occurs when the oil in the engine settles and accumulates in the bottom of the crankcase, causing the oil pump to suck air instead of oil. This can lead to serious engine damage if not addressed promptly. Fortunately, there are several fixes available to Harley owners who experience oil sumping.

One of the most effective solutions is installing a new oil pump. Harley-Davidson has redesigned the oil pump for the 2020 models and newer, which comes as a stock feature. This new oil pump is the only solution to the oil sumping issue. However, it is important to note that not all Harley models are affected by the oil sumping issue, and it primarily affects the Milwaukee-Eight motor. But what else do you need to know? Keep reading and lets find out!


Understanding Harley Oil Sumping

Harley oil sumping is a common issue that many Harley riders face. It refers to the accumulation of oil in the crankcase of the engine, which can lead to a number of problems if not addressed properly. In this section, we will discuss what oil sumping is, the common signs of sumping, and the causes of oil sumping.

What Is Oil Sumping?

Oil sumping is a phenomenon where oil accumulates in the crankcase of the engine instead of returning to the oil tank. This can happen due to a variety of reasons, including a faulty oil pump, worn-out bearings, or a clogged oil filter. When oil sumping occurs, it can lead to a number of problems, including reduced engine performance, increased oil consumption, and excessive heat buildup.

Common Signs of Sumping

There are several signs that can indicate that your Harley is experiencing oil sumping. These include:

If you notice any of these signs, it is important to take your Harley to a qualified mechanic as soon as possible to diagnose the problem.

Causes of Oil Sumping

There are several factors that can contribute to oil sumping in Harley engines. Some of the most common causes include:

  • Faulty oil pump: A faulty oil pump can lead to reduced oil pressure, which can cause oil to accumulate in the crankcase.
  • Worn-out bearings: Worn-out bearings can cause excessive oil leakage, which can lead to oil sumping.
  • Clogged oil filter: A clogged oil filter can restrict oil flow, which can cause oil to accumulate in the crankcase.
  • Wet sumping: Wet sumping occurs when oil accumulates in the engine’s lower end due to gravity. This can happen when the engine is not started for a long time, or when the oil pump is worn out.

In conclusion, understanding the causes and signs of oil sumping is crucial for maintaining the health of your Harley engine. If you suspect that your Harley is experiencing oil sumping, it is important to take it to a qualified mechanic to diagnose and fix the problem.

Harley-Davidson Engine Overview (And Their Relation to Oil Sumping)

Harley-Davidson is a well-known name in the motorcycle industry, and their engines are renowned for their power and reliability. The Harley-Davidson engine is a V-twin engine that is air-cooled and features pushrod valve actuation.

Milwaukee-Eight Engine

The Milwaukee-Eight is the newest engine from Harley-Davidson, first introduced in 2016. It features four valves per cylinder, a single camshaft, and a counterbalanced crankshaft. The Milwaukee-Eight engine is available in three displacements: 107 cubic inches (1753cc), 114 cubic inches (1868cc), and 117 cubic inches (1923cc).

Engine Oil System

The engine oil system is an essential part of any engine, and the Harley-Davidson engine is no exception. The engine oil system in a Harley-Davidson engine is responsible for lubricating the engine’s moving parts, reducing friction, and dissipating heat.

One issue that has been reported in some Harley-Davidson engines, including the Milwaukee-Eight, is oil sumping. Oil sumping occurs when oil accumulates in the crankcase, causing a loss of oil pressure and potentially damaging the engine.

To address this issue, Harley-Davidson has developed a fix that involves installing a new oil pump, which comes standard on 2020 and newer models with the Milwaukee-Eight engine. Additionally, there are aftermarket solutions available, such as a Mary vent kit, which is easy to install and inexpensive.

How To Diagnose Sumping Issues

If you suspect that your Harley-Davidson motorcycle is experiencing oil sumping issues, there are a few steps you can take to diagnose the problem.

Inspection Process

To begin, the bike should be run until the engine oil is at operating temperature. Once the oil is heated, the bike should be placed in an upright position, and the crankshaft position sensor should be removed.

If there is oil present in the sensor cavity, then it is likely that the bike is experiencing oil sumping. However, it is important to note that this is not the only cause of oil in the sensor cavity. Other possible causes include overfilling of the oil tank, a damaged oil tank cap, or a damaged oil pump check valve.

Tools and Products for Diagnosis

To diagnose oil sumping issues, there are a few tools and products that can be helpful. A crankshaft position sensor removal tool is necessary to remove the sensor during the inspection process.

Additionally, a compression tester can be used to check the compression of the engine, as low compression can be a sign of oil sumping. A vacuum gauge can also be used to check for vacuum leaks, which can contribute to oil sumping.

It is important to note that not all oil-related issues are caused by oil sumping. Other possible causes include oil leaks, overfilling of the oil tank, and a damaged oil pump check valve. If you are unsure of the cause of your oil-related issues, it is recommended that you take your bike to a qualified mechanic for diagnosis and repair.


Harley Oil Sumping Fix Procedure

Oil sumping is a common issue in Harley-Davidson motorcycles, which can lead to engine damage if not addressed in time. Fortunately, there are several solutions available to fix oil sumping, including oil pump replacement, seal and gasket solutions, and engine breather upgrades.

Oil Pump Replacement

Replacing the oil pump is the most effective solution to fix oil sumping in Harley-Davidson motorcycles. The new 2020 Harley oil pump comes stock on those 2020 and newer Harley models with the Milwaukee-Eight motor. The new oil pump design is meant to prevent oil sumping and improve engine performance.

Seal and Gasket Solutions

Seal and gasket solutions are also available to fix oil sumping in Harley-Davidson motorcycles. The main cause of wet sumping with this style of oil pump is that the check valve doesn’t close. The valve includes a ball bearing and spring, and it is sealed with a slotted cap screw on the top left of the oil pump. With this style of oil pump, it is common to blow some amount of oil out of the breather after sitting for long periods of time. Replacing the seals and gaskets can help prevent oil leaks and improve engine performance.

Engine Breather Upgrades

Upgrading the engine breather is another solution to fix oil sumping in Harley-Davidson motorcycles. The engine breather is responsible for venting excess pressure from the engine crankcase. If the engine breather is clogged or malfunctioning, it can cause oil sumping and other engine problems. Upgrading the engine breather can help prevent oil leaks and improve engine performance.


Aftermarket Solutions to Oil Sumping

If you are looking for a more permanent solution to your Harley oil sumping issue, there are a few aftermarket solutions available. Here are some of the most popular ones:

Upgraded Oil Pump Kits

One of the most common solutions to the Harley oil sumping issue is to install an upgraded oil pump kit. These kits come with a new oil pump body and cam gearcase, which are designed to improve oil flow and prevent oil from pooling in the crankcase. Some kits also come with a new crankcase breather, which can help to reduce oil blow-by and improve overall engine performance.

Breather Mods and Fixes

Another common solution to the Harley oil sumping issue is to install a breather mod or fix. These modifications are designed to improve the flow of air and oil vapor through the engine, which can help to reduce oil blow-by and prevent oil from pooling in the crankcase.

One popular breather mod is the S&S Cycle Stealth Air Cleaner Kit, which replaces the stock air cleaner and breather system with a high-flow air filter and breather. This kit is designed to improve engine performance and reduce oil blow-by, which can help to prevent oil sumping.

Overall, if you are experiencing oil sumping issues with your Harley, there are a number of aftermarket solutions available that can help to improve oil flow and prevent oil from pooling in the crankcase. Whether you choose to install an upgraded oil pump kit or a breather mod, be sure to do your research and choose a solution that is specifically designed for your Harley model and year.


What are the common indicators of oil sumping in Harley Davidson motorcycles?

Oil sumping can cause various problems such as excessive oil consumption, engine overheating, and decreased performance. Some common signs of oil sumping in Harley Davidson motorcycles include oil leaks, oil pressure fluctuations, and abnormal engine noises.

Which aftermarket kits are recommended for fixing oil sumping issues in Harley engines?

There are several aftermarket kits available for fixing oil sumping issues in Harley engines. Some of the popular ones include S&S Cycle Oil Pump Kit, Feuling OE+ Oil Pump, and Zipper’s Red Shift Oil Pump. It is recommended to choose a kit that is compatible with your Harley model and engine type.

How can one prevent wet sumping in older Harley models?

Wet sumping is a common issue in older Harley models, which occurs when oil accumulates in the bottom of the engine when the motorcycle is not in use. To prevent wet sumping, it is recommended to start the engine at least once a week and let it run for a few minutes. This will circulate the oil and prevent it from settling in the bottom of the engine.

What improvements were made to the Harley M8 oil pump to address sumping?

To address sumping issues in Harley M8 engines, Harley Davidson made several improvements to the oil pump. The new oil pump features a larger rotor and a redesigned scavenge port, which improves oil flow and reduces the chances of oil sumping.

Can a faulty oil pump cause sumping, and how can it be diagnosed?

Yes, a faulty oil pump can cause sumping in Harley Davidson motorcycles. Some common symptoms of a faulty oil pump include low oil pressure, engine overheating, and abnormal engine noises. To diagnose a faulty oil pump, it is recommended to perform an oil pressure test and check for any oil leaks.

What are the steps for properly installing an oil sumping fix kit?

The steps for installing an oil sumping fix kit may vary depending on the kit and the Harley model. However, in general, the installation involves removing the old oil pump and installing the new one, along with any other components that come with the kit. It is recommended to follow the manufacturer’s instructions carefully and seek professional help if needed.