Finding & Fixing Harley Oil Leak Between Engine And Transmission

Harleys are unreliable. Especially, Harleys weigh more and cost more. Harleys are oil-leaking pieces of junk. If Harley leaks oil, it marks its spot. Some people say that. But is it true?

These are some of the common criticisms. However, the Harley oil leaks between the engine and transmission, and it’s true. But you may wonder how to fix Harley oil leaks between the engine and transmission.

You can find some common leak points, such as internal primary seals, rocker boxes, and main transmission seals. Thus, it would help if you handled all the leaking issues. To fix Harley Davidson oil leak problems, read on.

What Is Leaking Between Engine And Transmission On Harley?

Though your Harley has the best and most unique design, it’s still a motorcycle. And every bike can leak oil, especially if some component is faulty.

Harley’s engine does not leak oil. Early Harleys used an automatic lubrication system that pulled out oil from an oil pump for primary chain lubrication. The oil leak from the motorcycle appears to be excess oil leaking from the primary chaincase.

Oil would drain from the primary chain into the primary chaincase. With a drain hole, the oil drain to the floor. The resulting puddles on the floor lead people to believe Harleys is leaking oil. You can also find oil leaks on gaskets and plugs without leaks from the air cleaner and primary chain case.

Harley Oil Leak Between Engine And Transmission

How To Fix Harley Oil Leaks Between Engine And Transmission?

To fix your Harley oil leaks between the engine and transmission, you should do the following:

  1. Start the motorcycle and ride it until it reaches the operating temperature. Park your bike on level ground. With a 10mm wrench, remove the battery negative cable bolt. Pull the negative battery cable from the battery post. Pull the zip tie and collapse it.
  2. Now you should take off the clutch and compensator assemblies with adjustment screws. It would help if you took some snap ring pliers and now pop out the retaining clip. Now pull it here to see the contrasting thread.
  3. It would help if you lost all these tabs with this bolt that holds the inner primary. It would help if you did the same thing with a starter jackshaft. Do the jackshaft assembly and go the other way, and loosen or remove the starter.
  1. Furthermore, come back and close all the primary bolts. Pull the seal after getting the leak. Usually, you do it with self-tapers. If you are out of it, you can do it with sheet metal screws that will work well. You will put two of them. Carefully you want to do this because you don’t want to hit the bearing.
  1. And, now you can see there are no marks and everything is fine. Let’s seal it back up, and you have a new seal here. To prevent it from leaking, you will need some grease. Pour it with oil.

How To Make Sure Your Harley Davidson Doesn’t Leak oil?

To prevent oil leaks on your Harley motorcycle, you can take some steps:

Ride Your Bike Regularly:

It may sound simple, but it goes a long way in preventing motorcycle oil leaks. Long periods of disuse will quickly wear out your gaskets and oil.

For a better example, think of the gasket as a rubber band. Additionally, if you don’t use your motorcycle, your gasket becomes weak and breaks easily. Nonetheless, the more you use it, the longer it will last.

Therefore, this applies to gaskets. New gaskets will increase body defects, which will undoubtedly lead to leakage.

Regularly Change The Oil

Did you know that your motorcycle’s old oil can corrode the engine? Leaving old oil in your engine can also damage engine gaskets. Old oil contains acidic components, which can eat away gaskets and cause holes.

Engine oil has additives that prevent the oil from becoming acidic over time. It’s right. Engine oil comes with additives that prevent any form of acidity. But these additives dissolve over time, and acid components form in the oil.

Read: How Often To Change Motorcycle Oil

Routine Inspection

To prevent significant leaks on your Harley, you should discover all leaks before they become problems. And you can do it if you inspect your bike after a hard ride and a long run.

Check all motorcycle parts and look for oil stains or signs of possible oil leaks. Be thorough. Sometimes oil leaks in an inconspicuous place and exhausts when the bike cools down. Hence, you may only find them once the oil leaks are more significant.

Related Questions

Harley Leaking Oil After Sitting?

You may know Harley motorcycles have three separate compartments for oil: engine, primary, and transmission. Because Harley motorcycles have three separate compartments, the engine will have more seals and O-rings than other brands. Mainly, this expands the chance of leakage after sitting.

After the Harley sits for a while, the seals can dry out and shrink. And it releases minor gases between adjacent engine elements and develops small leaks or drips.

It isn’t delightful to find oil dripping under your motorcycle. Indeed, if you can find the source of the leak, it’s best to take a ride, and then the oil will clean. Come back and see if the motorcycle has stopped leaking.

Harley Leaking Oil At Head?

Let’s explore your Harley leaking oil around the head. Take a closer look at the motor. Notice where the head begins, and the cylinder ends. You may notice oil coming from the part of the V-twin.

There is a thin gasket that has failed. Any number of items can affect this causing you problems. The question is, what do you do now? Should you ride a bike?

The obvious answer is to fix it. Depending on how the leak is, you want to avoid putting it on the road. Please think. If your rear tire leaks, it can make perfect conditions for an accident. So yes, you should only run it if the leak is minor.

Harley Oil Leak Right Side?

There are various possibilities for oil on the right side of the Harley. Additionally, one could be an oil filter problem, as you mentioned. Another could be a pushrod tube o-ring leak.

One at the top, bottom, and middle could be a rocker box gasket leak. Even so, it could also be a lifter block gasket; the leak could also be a lifter block gasket leak. Moreover, another could be due to crankcase venting.

Neither would be considered “normal” but could arise. You would wash the bike reasonably well to get rid of the oil that is now there. Then take the bike back for a ride. Note where the oil is and then track it back to where it is boiling.

Why Did Old Harleys Leak Oil?

Old Harleys don’t leak oil. This is just the way the lubrication system was designed. Before Harley’s reintroduced oil system (1936-1938 for change dates depending on model), they used a total loss system. Harley’s slogan is: “Why use dirty old oil when you can get fresh oil every time?

Final word:

Finally, there are Numerous reports of oil leaking from seals between the transmission and engine. If it’s just soaked with oil, clean it with some green dye and rinse.

Look to show up again how long it takes. If it leaks, you must repair it if oil damage or leakage is noticeable. Overall, you may know how to fix Harley oil leaks between the engine and transmission. We hope you can fix your Harley oil leak problem quickly—best of luck.

Read Also: Harley Transmission Oil Change


Rio is a car & motorcycle mechanic who is working with different kinds of problems relating to oil and grease. He is also a passionate technical writer.

Recent Posts