Why Is My Motorcycle Leaking Oil from the Exhaust?

Today, we’re going to look at the most common causes of motorcycle exhausts leaking oil.   

If you see your motorcycle’s exhaust leaking oil, it could be due to any number of reasons. We’ll go over the most common scenarios and our recommendations on how to fix each one. 

Whatever the case, oil leaking from your motorcycle’s exhaust is a concern and should be fixed on the double! If left unattended, it could lead to more problems down the line. 

We have been working on motorcycles for over a decade and riding for even longer. You came to the right place if you need help figuring out a solution for a motorcycle exhaust leaking oil. 

Keep reading for more info about motorcycle exhausts leaking oil. 

What causes oil leaks from a motorcycle exhaust? 

Let’s look at some possible reasons why your motorcycle’s exhaust is leaking oil. 

Faulty or damaged engine gasket 

This is the most common reason for oil leaks from a motorcycle exhaust. Your motorcycle’s engine uses various gaskets to make a tighter seal between components. These gaskets are designed to withstand high pressure and even higher temperature. However, they can get wear and tear and get damaged over time. This is especially prevalent in older motorcycles. 

A damaged gasket could cause oil to leak into the combustion chamber. This will lead to oil leaking into the motorcycle exhaust, where it will produce black smoke upon burning. The damaged gasket can cause oil to leak directly into the exhaust in some cases. 

Usually, the gaskets with the highest chances of getting damaged and leaking are the oil pan gasket, valve cover gasket, cylinder head gasket, or the crankcase gasket. These gaskets are exposed to the most pressure, and it is easy for oil to leak out, especially if the gaskets are old and worn. 

Fix: Replace the gaskets

If a gasket is damaged to allow oil to leak into the motorcycle’s exhaust, the only fix is to replace it with a new one. The new gasket will make a tighter seal that will hold up better to high pressure. 

Although gaskets age and degrade over time, the process is expedited in a bike that doesn’t get used regularly. This is because regular riding exposes the gaskets to different pressure and engine temperatures, allowing them to expand fully and make a perfect seal. 

If your bike has been in storage for the winter or you haven’t used it for a while, the gaskets have probably become less effective. Get them replaced, and you should be fine. 

Damaged oil plug

Another fairly common issue that leads to oil leaking from a motorcycle exhaust is an oil plug that isn’t working correctly. This could be the oil drain plug at the bottom of the oil drain pan, the valve cover plug, or the side crankcase plugs. 

An oil drain plug could have been damaged if you went over large bumps and the plug made contact with the road. Large stones or road debris kicked up by the tires could also be blamed. 

Furthermore, oil drain plugs could be leaking if they aren’t secured tightly enough. This may be due to user error while servicing the bike or excess vibrations from the motorcycle loosening the plug. 

These plugs also use O-rings that can degrade over time, causing oil leaks. 

Fix: Replace or tighten oil plugs

If a faulty oil plug is to blame for the oil leaking from your exhaust, you should get it replaced ASAP. Even if the plug isn’t tightening correctly, replacing it’s a good idea as it could become even looser over time. 

Incorrect engine oil

This problem isn’t as common as the others on this list. However, suppose you accidentally added the wrong type of engine oil to your motorcycle on its last service. In that case, it could cause an oil leak. 

Different motorcycles are meant to use different engine oils. Each engine oil has different properties that work well with specific engines. Your bike may be using the wrong type of oil that isn’t suitable for the engine. Under excess pressure and heat, it could leak out of the exhaust. 

Fix: Use the correct engine oil

This is an easy fix. Refer to your bike’s instruction manual to see which type of oil the manufacturer recommends using. Once you add the appropriate oil, the problem should subside. 

Worn piston rings

Last but certainly not least, we have worn or damaged piston rings. These rings go over the pistons in a motorcycle engine and make a tight seal. Over time, these rings can wear and tear to the point that they no longer function properly. 

If that is the case, oil leaks from the exhaust are the least of your problems. Loose piston rings can cripple an engine and leave it completely unusable. Worn piston rings can cause significant damage to sensitive internal engine components. 

If you have worn piston rings, you might see oil leaking from the exhaust. Excessive black smoke is another indicator of damaged piston rings. Poor acceleration and depleting oil supply could also point to piston ring failure. 

Fix: Get professional help

If you suspect your engine’s piston rings of being faulty, it is best to seek professional help. Unless you are really comfortable working on an engine and have a lot of experience, you probably won’t be able to fix this problem on your own. 

Furthermore, if your bike’s piston rings are worn, don’t even ride it. Take it to the shop on a flatbed if you have to because running the engine will exacerbate the problem. 


Oil leaking from a motorcycle exhaust could be due to any number of reasons. However, the most common issue is a faulty gasket or O-ring that prevents engine parts from sealing correctly. 

While you can diagnose and solve some of these problems on your own, it is recommended that you take the bike into the shop for more severe issues like worn piston rings.

Hugo Alais

Hi, I'm Hugo, I'm a motorcycle enthusiast who’s been riding for the last 10 years. I'm passionate about all things motorcycles and started Bikes Future to help other riders make the right motorcycle moves. I ride a white Kawasaki Ninja 400. You can find out more about me and my experience with motorcycling here.