Reasons why your bike gives out smoke

Reasons why your bike gives out smoke

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If your bike is giving out excessive smoke, then this could be a worth noticing issue.

Different colors of exhaust smoke points out different issues with your bike.

So, have a look at all these three types-


1. Black exhaust smoke


Black exhaust smoke means a sign of damage. It points to some very critical issues with your bike engine or carburetor or blocked air filter.

Incomplete combustion of fuel releases black exhaust smoke. This incomplete combustion will lead to a release of carbon which is black colored.

There could be more than one reason for the incomplete combustion of fuel.

  • There might be a clogged air filter.

Oxygen is necessary for combustion, and a clogged air filter would not deliver sufficient oxygen for combustion. Hence, this will lead to incomplete combustion.

The solution to a clogged air filter is simple; you have to either clean it or replace it with a new one if there is a total blockage. 

  • The second reason for incomplete combustion can be a clogged carburetor. 

 A carburetor delivers air/fuel mixture to the combustion chamber. If the combustion chamber is faulty, it will not provide the appropriate air/fuel mixture. The difference in ratios of their quantity will lead to incomplete combustion of fuel. This incomplete combustion will further release black smoke due to the presence of carbon in it. 

The solution to a clogged carburetor is simple; you have to clean it thoroughly. 

  • The third reason could be engine issues. 

Over time, the deposition of substances occurs on the walls of the engine. When you ride your motorcycle, this deposition gets mixed with fuel and can cause an interruption to the combustion of fuel. This interruption will lead to incomplete combustion of the motorcycle fuel. Hence it will eventually lead to black smoke. 

The deposition could be of oil residue or minute metal particles.

The solution to this issue is not easy; you have to take your bike to a trained mechanic or book a service at MEKVAHAN

  • A faulty catalytic converter also leads to black smoke. 

Although, the work of a catalytic converter is to convert the harmful gases and carbon produced during combustion to less toxic gases.  In case of a faulty catalytic converter, the exhaust system will emit black carbon smoke. In this way, a faulty catalytic converter also causes black smoke.

The solution to a faulty catalytic converter is that you have to change it.


2. The second type of exhaust smoke is white-colored smoke.


White-colored smoke can be usual, or it could be due to some mechanical issue. If a bike stays parked for a long time, then while starting it, you may notice white smoke.

Now, in this situation, you need not worry much. It might be because of the evaporation of water vapor. When a bike stays parked for a long time or in a garage on a winter night, water droplets accumulate in the exhaust or the inner components of the exhaust system.

When you start your bike engine, hot exhaust gases vaporize this water, and this, in turn, creates white smoke.

This smoke due to water vapor generally disappears within 30 seconds or 1 minute. If it doesn’t happen, then there is some other issue.

The other issue worth worrying about is that motorcycle coolant has made its way into the bike’s combustion chamber.

Motorcycle coolant can reach the combustion chamber due to several issues such as defective cylinder head gasket or cracks in the cylinder head.

How would you know if the coolant is making its way to the combustion chamber?

It’s a simple check for the coolant level or any discoloration of the coolant.


Well, this damage will cost you a lot. You will have to change the defective cylinder head gasket, and even worse, if you have cracks in the cylinder head, you have to replace it with a new one.

Also Read: How to do a bike service at home


3. The third type of exhaust smoke is blue/grey smoke.


Similar to black exhaust smoke, blue/grey smoke is also a sign of something more serious. The engine generally emits Blue/grey smoke when the motorcycle engine oil enters the combustion chamber.

In this case, your combustion chamber will have a mixture of air+fuel+engine oil which means engine oil will burn along with the motorcycle fuel in the combustion chamber.

This burning of engine oil releases blue/ grey smoke. There are many possible damages due to which engine oil enters the combustion chamber. A clogged or dirty PCV valve or wear and tear of the piston ring allows oil to enter the combustion chamber. 

Apart from these issues, valve seals could have worn out, causing engine oil to enter the combustion chamber.

You can check for this issue by removing spark plugs. If you found any oil deposition on the tip of the spark plug or in the spark plug socket, then this is a clear symptom that oil has made its way to the combustion chamber.

Apart from these issues, other issues arise due to the negligence of the rider.

Using lower grade or incorrect engine oil also causes an engine to emit exhaust smoke.




These are the various reasons why your bike is emitting excessive exhaust smoke. If you are facing any such problems with your bike, then look out for these issues and if you are unable to find any issue, Book a bike service at MEKVAHA

Mukesh choudhary
Mukesh choudhary
Age may offer experience but my passion for cars brings me expertise. I am extremely good at one thing and that's writing about cars.

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