Why is My Dirt Bike Smoking?


There are various reasons why a dirt bike engine has white, blue or grey smoke. The most common reason is the burning oil problem. Other reasons are malfunctioning power valve, damaged piston rings, a bad spark plug or rich fuel condition. The smoke of the dirt bike can be due to excessive clearance between the valve guide and the valve stem. 

Seeing excessive smoke from your favourite dirt bike can make you sad. You cannot ignore these issues because they can sign some severe faults in your bike. Smoke coming from the motorcycle explains that your engine is not working correctly. There are different types of issues are there which can create trouble for any rider.

Leaking of oil in a dirt bike is almost an irritating issue which anyone would not like to welcome and wish to get rid of it; bogging out of a dirt bike engine is also one of the issues of the dirt bike.

But here today, we are talking about smoking issues on a bike, and you can also understand different aspects of this and how much should two-stroke smoke is also a standard query that is frequently asked.?

Why is your Dirt Bike Smoking?

One of the reason we can say for smoke coming from the exhaust of dirt bike is piston rings. The piston ring’s function is to separate and avoid mixing of lubricant with the air-fuel mixture in the engine.

Due to friction, when the piston rings wear out, the air-fuel gets to mix with the lubricant oil in the combustion chamber, and it causes terrible combustion and starts giving out smoke from the exhaust of the dirt bike.

Many factors cause smoking on a Dirt bike. We can find out by checking the colour of the bike.

Black Smoke

The black smoke emitted from the exhaust is generally nothing to worry about and is connected with the equal balance of the combustion control by the ECU. The black smoke is due to an overly rich fuel mixture created when the air-fuel ratio descends below the optimum ratio of the spark.

The ignition can only combust a small amount of fuel in a cycle, so unburnt fuel is pushed out into the exhaust system, and it’s combusted downstream of its combustion chamber.

The reason behind these conditions can be a leaking fuel injector, a blocked fuel return pipe, broken oxygen, airflow sensor, a fuel pressure regulator stuck closed.

A dirty air filter will also prohibit pure air from going through to the combustion chamber.

It constricts the volume of air entering the cylinder. It will also make for less efficient combustion.

Blue Smoke

You can see the blue looking smoke in dirt bikes that have unwanted oil mixing with the air-fuel mixture. It means there’s a contaminant with the cylinders and their combustion along with the air and fuel.

This cross-contamination is caused by the engine where the cylinders, Pistons and valves along with failed seals.

A damaged valve stem seal or guide will also allow the oil to make its way down from the valve train above the cylinder head.

While a damaged piston ring will allow oil from the crankcase to squeeze its way upwards and into the cylinders, the differing pressures within the combustion chamber throughout the engine cycle will lead to oil being sucked through any leaks in the same way that the air-fuel mixture is sucked in via the opening of the inlet valve.

It can lead to a lack of compression within the cylinders and increased pressure within the crankcase resulting in decreased power.

Blue smoke can be standard in most dirt bikes; by turning up the power output in an engine, more stresses apply to each component is increasing.

The possibility of oil leaks turbochargers themselves can also fail to allow the oil used to lubricate the turbine to spill from bad seals into the cylinders along with the compressed air adding to the air-fuel mixture contamination.

White Smoke

White looking smoke probably isn’t smoke at all, but steam and this can potentially be nothing terrible, or you could be a mile or two away from an engine replacement.

You may notice that from a cold start, white smoke will emanate from the exhaust tips. It is nothing to worry about, and It is created by vapour from combustion.

If your dirt bike is fully warmed up, the ambient temperature is reasonable, and if your bike is still producing steam. However, you could be looking at head gasket failure or even a cracked cylinder head or block from overheating.

The head gasket is designed to keep the oil and coolant systems apart. Cementing the cylinder head and combustion chambers together with a split in the gasket will send liquids into places they shouldn’t be. If a head gasket fails in a particular area, a coolant will enter the cylinders.

The engine will then try to compress and combust water, leading to potentially catastrophic engine damage and steam pouring out of the exhaust.

The size of the leak will dictate how much steam is produced but often, when a head gasket fails, you won’t be able to see out of the back window due to your bike suddenly morphing into an actual steam engine.

Bike with 4-stroke engines:

The white smoke that comes from the exhaust of the Dirt bike means in the combustion chamber the engine oil is leaking where the petrol gets burnt.

So along with petrol engine is now burning engine oil. The white smoke is produced by burning engine oil. It means that you have changed your piston and the piston rings that prevent the engine oil from leaking into the combustion chamber.

Bike with 2-Stroke Engines:

2T is known as engine oil in 2-stroke bikes. Directly into the fuel tank, the oil is mixed with petrol. So the petrol and oil are burnt by the engine together.

The reason behind white smoke in this means that the mixture of oil and petrol is not correct and you have extra oil than the required amount. Always be careful with the mix of oil.

How to Fix White Smoke in Dirt Bike?

Step 1: Ambient Temperature

First, check the ambient temperature level in your bike because it plays a vital role in smoking. If the temperature is less than 50 degrees Fahrenheit, then white smoke is regular until the warm-up of the bike’s engine. If the white smoke issue is still there, there is a possibility of excess water in the machine.

Step 2: Inspect

Seals, pistons, and head of cylinder may be the reason for overheating and causing smoke. So inspect those things properly. If you don’t know about the bike parts, seeking professional assistance will be best. Your doing something wrong can make the issue more worst.

How to Fix Black smoke in Dirt bike?

Step 1: Air Filters

Sometimes blockage in the Air filter leads to stop reaching the sufficient in your bike’s engine and hence more fuel burns. So this can be one of the reasons for black smoke. Inspect the air filters and if there is sometimes stuck so clean them correctly or can also replace them if needed and, lastly, ensure time to time if they are okay.

Step 2: Piston Rings

Your bikes piston rings should be inspected and ensure that it is good in condition. The work of the piston is to avoid the infiltration of engine oil inside the combustion chamber of your bike’s engine. So this can also be the reason for black smoke in your dirt bike.

Step 3: Fuel Additives

To avoid the black smoke on the bike. Use suitable fuel additives to reduce the economy of fuel and make the engine’s performance lower.

How to Fix Blue or Gray Smoke in Dirt bike?

Step 1: Inspect Spark

If you see blue or grey coming from your dirt bike, check the spark plugs correctly, and if it’s not in good condition, it’s better to replace it with the new one.

If you see black soot on the spark plug of your dirt bike, then it can be a sign of a high mixture of fuel or air if there is a shiny wet black film on the spark plug. So it can be a sign of excess oil.

Valve seals and piston rings should be inspected and ensured that they are not loose; they should be airtight. Sometimes the failure of seals leads to the blue and grey smoke in your dirt bike.

So it is suggested to replace it as soon as possible. If you don’t have any idea about that, so seek personal assistance, or also you can read the user manual for guidance.

Warnings:

Suppose you see smoke coming from your dirt bike and are not aware of what causes it exactly. So it’s better not to ride the bike till it stops smoking and runs better.

If you don’t know about the bike parts, it is advisable not to repair any part of the bike yourself because a small mistake from you can create a big issue. Visit any professional bike repairs and let your bike fixed in the best way.

Thomas A. Talley

I’m Thomas. Since childhood, I am fond of bikes and hence dirt bikes are my passion now. Ever since then, I’ve been giving advice to the beginners and this has become my hobby.

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