Why Do Harleys Leak Oil?


If you’ve ever wondered why Harleys leak oil, this article is for you. The answer is simple: they have a poorly-designed automatic lubrication system. Instead of the traditional oil pump, Harley engineers installed a tube in the back half of the chain cover so that the oil would drip over the primary drive chain and collect in the primary clutch case. From there, the oil would be drained to the ground. While this system is effective, it has been mocked by many critics who don’t know about the system and instead take a Harley to be the epitome of “big old oil leaks”.


The best way to find out if your motorcycle has a Wet-sump is to check your oil pan. If the plug is not tight enough, oil can leak into the pan. The vibrations of riding a motorcycle can also cause it to become loose. Ultimately, the oil drain plug will lose its effectiveness and will leak. When this happens, the first step is to clean up the oil.

Another cause of Harley oil leaks is the crankcase breather. If there is a leak in the crankcase, the oil can blow out the breather and end up on the piston skirts. The engine may also smoke because of too much oil. A wet-sump problem occurs in older motorcycles, like Harley Sportsters and softails. It typically happens after extended non-use. Fortunately, this problem is easily remedied.

Rocker box

A Harley leaks oil for a number of reasons. Some Harleys have a total oil loss system, where oil is injected into the valve system, which then leaks outside the engine and falls to the ground. Other Harleys can leak oil through the primary cover, the oil pan, or even the starter area. Leaks can also originate in the engine’s external oil lines. Regardless of the cause, it’s important to investigate the source.

In the 1930s, Harley engineers designed their motorcycles with a total-loss oiling system. Oil would drip onto the primary drive chain and collect in the primary chaincase before draining to the ground. However, oil still leaked from these motorcycles because they were made to be hard-working machines in an era before interstate highways. To remedy this problem, Harley engineers developed a scavenging pump that would pump oil away from the bottom of the bike and return it to its oil tank.

Air cleaner

A dirty air cleaner on your Harley may indicate an issue with your bike’s engine. When the engine is hot, oil is sucked through the breather tube and dropped into the air cleaner. These droplets fall back to earth when the bike is standing still, but spray back into the air filter when it’s moving. This happens because Harley’s air cleaners are designed to piddle oil. When you notice the oil spraying back into the air filter, you can fix it by replacing your air cleaner with a new one.

The best air cleaner for Harleys is KN brand. The KN brand filters will restore your bike’s original red color. The backing plate is held on to the motorcycle by three small screws and two large bolts. If it’s rusted or dry rotted, oil will leak all over your engine. A rusted air cleaner housing will let oil out of the engine and into your passenger and rider’s clothing.

Engine gaskets

One of the most common reasons why Harleys leak oil is a failing head gasket. When this occurs, the exhaust is forced backward, and the engine runs hotter than it should. Other causes include worn throttle shafts, cracked vacuum lines, and external oil and coolant leaks. Check your bike for these signs to determine if a head gasket is causing your motorcycle to run hotter than normal.

The problem may be a faulty gasket on the rocker cover or valve cover, or an internal engine defect. In either case, the engine will leak oil if the gasket is not installed properly. Another possible source of oil leakage is the primary cover, drain plug, or starter area. External oil lines may also be leaking oil, and it is important to fix them to prevent a leak from forming in the engine.

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