Motorcycle smoking from the engine is a common problem that can be caused by a variety of factors. The smoke produced by a motorcycle engine can be white, blue, or black – each indicating a different problem. Understanding the causes and potential consequences of motorcycle smoking from the engine (or the exhaust) is crucial for maintaining the health of your bike and ensuring a smooth ride.
In this article, we’ll take a look at all of the possible reasons why your motorcycle is smoking from the engine. Let’s get started!
Understanding Different Smoke Colors and Their Causes
Luckily, diagnosing smoke coming from the engine is quite easy, since you can roughly guess what the issue is just by looking at the color of the smoke. Burning coolant, oil, and petrol produce a different color of smoke, and it’s what will help us diagnose the issue.
Below, we will take a quick look at the different color and smell of smoke that might come from the engine and from the exhaust.
White Smoke From the Engine: Coolant Leak
White smoke is usually caused by coolant leaks, which can occur due to a cracked cylinder head, blown head gasket, leaky coolant hose, etc. This type of smoke is accompanied by a sweet smell (a very important clue) and can indicate a serious problem if it’s coming from the exhaust. If the white smoke doesn’t smell sweet, then it’s probably not a coolant leak.
If the white smoke is coming straight from the engine area and not the exhaust, then your bike probably has an external coolant leak. In that case, coolant drips down onto the scalding hot engine or the exhaust headers, boils off and evaporates, thus causing white smoke. Luckily, external coolant leaks are most often a cheap and easy fix.
Lastly, remember that white smoke while the engine is cold is completely normal – it’s simply water vapor and will disappear once the engine and the exhaust pipe warms up. If it does not disappear, then it might indicate coolant burning inside the combustion chamber.
Blue Smoke From the Engine: Oil Leaks
Blue smoke is typically caused by worn valve guides, worn piston rings, worn cylinder walls, and oil leaks. As the valve guides wear, they can allow oil to enter the combustion chamber and be burned along with the fuel. Similar story with worn piston rings and cylinder walls – they allow oil to pass through into the combustion chamber and then it gets burnt with fuel, thus causing black smoke.
If you see blue smoke coming from the engine itself and not the exhaust pipe, then your bike probably has an external oil leak, which is most often due to a leaking valve cover gasket. In most cases, it’s an easy and cheap fix.
Blue smoke is often accompanied by a burning oil smell that is distinct and strong.
Black Smoke From the Engine: Rich Air-To-Fuel Mixture
Black smoke is typically caused by a rich air-to-fuel mixture, which can be a result of many factors, such as a bad spark plug, poor carb synchronization, a leaky injector, etc. Since black smoke is usually caused by a rich mixture, it produces a very strong unburnt fuel smell that is extremely dangerous and can sometimes cause a burning feeling to your eyes.
If you see black smoke coming from the engine area, then it might be due to an exhaust leak, or due to plastic or other debris burning on the hot engine fins.
Smell – An Extremely Important Clue When Troubleshooting Engine Smoke
Now, while most articles and videos on the internet emphasize the importance of the color of the smoke, the smell of the smoke can also play a huge role in helping you diagnose the issue. Personally, I primarily use smell to diagnose engine smoke and it has never failed me so far.
Of course, describing a smell through text or through video can be very difficult, so it might be a good idea to experience the difference between the smell of burning coolant and oil yourself. Obviously, it must be done in a safe manner, as inhaling burning oil and coolant vapor is harmful.
How to Prevent Engine Smoke on Motorcycles
Regular maintenance and inspection are essential in preventing smoking from the engine. Checking the air filter, inspecting the fuel system, visually inspecting the engine itself, and performing a compression test are all important steps in identifying the cause of smoking from the engine. These steps should be taken at regular intervals to ensure that your motorcycle is running properly.

If you notice smoke coming from your motorcycle engine, it is important to take action to address the problem as soon as possible. Ignoring the issue can result in poor gas mileage, engine failure, and in the worst-case scenario – fire (if the leak is external).
Is It Safe to Ride a Motorcycle That’s Smoking From the Engine?
Now, if there is smoke coming from your motorcycle’s engine, you might be wondering whether it’s safe to ride.
Well, if the smoke is coming from the engine area itself (engine fins, headers, etc.), then it would be a good idea to fix the issue first in order to avoid the small chance of whatever is burning catching on fire. The chances are low, but it is better to be safe than sorry.
But if there’s smoke coming from the exhaust, then your bike’s engine most likely has an internal problem, which can be quite costly to repair. In that case, the worst that can probably happen is your engine might seize or start knocking after a while of ignoring the issue.
Final Thoughts
Motorcycle smoking from the engine is a common issue that many riders have to face eventually. Whether it’s due to an external oil leak due to a failed gasket, a coolant leak, or something else – it’s always a good idea to fix the issue ASAP.
The color of the smoke can be a great help in diagnosing the issue as it will point you in the right direction, but the smell can also be an accurate indicator of what is actually wrong with the motorcycle.
Thanks for reading and we hope you’ve found this article useful. If you have any suggestions or questions, feel free to contact us.

Nick Kowalski is a diesel mechanic by trade, but his passion lies in motorcycles.
He’s been riding them since he was just a wee lad, and he loves restoring old Japanese street bikes and ATVs in his spare time.
Nick is an adrenaline junkie at heart, and he loves nothing more than hitting the open road on his motorcycle.