Here’s Why Your Motorcycle Exhaust Pipes Turn Blue

Motorcycle Exhaust Pipe

You have just noticed that the exhaust pipe of your motorcycle has turned blue and you are concerned on what caused this colouring and what to do about it.

Well, firstly there is no need for panic here.

You might have even come across people who proudly flaunt this blue exhaust pipe. However, for some it can be an annoying thing to see their exhaust pipe not in their natural colors.

So, why does motorcycle exhaust pipe turn blue?

The reason why a motorcycle exhaust pipe turn blue is because of the excessive heat going through the exhaust pipe. The metal forms an oxidized layer due to the extreme heat, which colors the exhaust pipe blue.

The main causes for this excessive heat are:

  • Lean air-fuel mixture in the engine
  • Ignition timing is off
  • Leaks in the exhaustion system
  • Exhaust pipe material is not right

To remove the blue color on the exhaust pipe, you can use products and solutions specifically designed for removal. All you need to do is apply the solution, wait for some time and clean them. The coloring will be removed.

Let us deep dive into each of these aspects one by one.

Why Exhaust Pipes Turn Blue?

The reason why your exhaust pipes turn blue is because of the excessive heat going through the exhaust pipes. The exhaust pipes are designed to withstand heat, however if there is too much heat with soaring temperatures, the exhaust pipe metal starts coloring.

The coloring is because of an oxidized layer forming on the surface of the metal exhaust pipe. The metal has higher oxidization temperatures. But, as the heat raises the temperature to extreme levels in the exhaust pipe, the metal starts to get oxidized.

Most exhaust pipes are made up of Stainless-Steel owing to their better performance in resisting heat and corrosion when compared to other metals.

Additionally, depending on the material used for exhaust pipe in your motorcycle and the temperature of the heat, the color changes accordingly. You may even see, gold, yellow, brown and in the worst case – red, if the metal is not able to withstand the heat.

What Causes This Excessive Heat In Exhaust Pipes?

The exhaust pipe turning blue due to extreme heat is not a big problem. However, the reason that is causing so much heat in pipes can also cause issues in the motorcycle.

In other words, you need to find what is causing this excessive heat.

The main causes for this excessive heat are:

  • Lean Air-Fuel mixture in the engine
  • Ignition timing is off
  • Leaks in the exhaustion system
  • Exhaust Pipe material is not right

#1. Lean Air-Fuel Mixture In The Engine

Lean Air-Fuel mixture refers to a low proportion of fuel in the engine for the air present. Rich Air-Fuel mixture on the other hand is when you have a high proportion of fuel for the volume of air present in the engine.

Now, when the air-fuel mixture is lean, there isn’t enough fuel to absorb the heat and combust to generate power. Air has to carry all this heat and flow through the exhaust system.

As a result, the excess heat flowing will cause the coloring of the exhaust pipe which you are seeing in the form of a blue pipe.

If air-fuel mixture is the problem, then you need to start inspecting the engine components starting from your carburetor.

#2. Ignition Timing Is Off

Another possible reason for this extreme heat could be when the ignition timing is off in your engine.

The ignition timing allows the spark plug to time the spark(ignition) properly based on the engine RPM. If the RPM is high, engine has to be ignited much earlier so that the engine can release bulk of the energy at the right time.

If the timing is off, there can be detonation or waste of power. This can also result in excessive heat passing through the pipe, which consequently is responsible for turning the pipe blue.

#3. Leaks In The Exhaustion System

Any kind of leakage in the exhaustion system can also cause extreme heat flowing through the exhaust pipes.

Leaks in exhaustion system are difficult to examine. You should take your motorcycle to your mechanic for inspection.

#4. Exhaust Pipe Material Is Not Right

If your motorcycle is new and you are seeing the coloring of exhaust pipe within few days of your purchase, then the material used for exhaust pipe is not the right fit.

Different materials have different resistance to heat and corrosion. While Stainless Steel is the most used metal for exhaust pipes, Mild Steel and Titanium are also used in different motorcycles.

 If the material used is indeed not the right fit, you can either use ceramic coating in the interior layer or you can choose to replace the material with a more suitable one. Either option requires some intensive labor. You need to take your motorcycle to a professional.

How To Remove The Bluing Of Exhaust Pipe?

If you don’t like the blue color on your exhaust pipe and wish to remove it, there is an easy solution.

There are cleaning and polishing products specifically designed to remove the bluing of your exhaust pipe. The polishing product removes the oxidized layer formed on the exhaust metal to get rid of the coloring.

All you need to do is – take the product or solution and apply them on your exhaust pipe – where the coloring layer has formed.

Here are the steps you need to follow:

  • Make sure the exhaust pipes are cooled down before applying the solution on it.
  • Apply the solution on the colored region of your exhaust pipe.
  • Allow some cool down period. Wait for some time for the solution to remove the oxidized layer.
  • Use water or grease – whichever is recommended – to remove the solution.
  • Dry it off with a cloth and now you will have your exhaust pipe back to its original form without any coloring.

Also note that, this solution, while removing the oxidized layer also causes rough finish on the metal surface. So, do not use the product too often on the exhaust pipe.

On the other hand, if you are okay with the blue color on your exhaust pipe, you need not worry. The oxidized layer formed on the surface will do no harm to the motorcycle. Rather, you need to inspect the cause of this coloring, which might cause damages if left unchecked.

How To Prevent The Bluing Of Exhaust Pipe?

Okay, you have cleaned the bluing on your exhaust pipe. But you don’t want this situation to repeat. So, you are wondering how can you prevent this coloring of your exhaust pipe from happening again?

Well, the preventive measures can include:

  • Finding the root cause of the heat
  • Using ceramic coating
  • Replacing the exhaust pipe material

#1. Find The Root Cause Of The Heat

The coloring of your exhaust pipe is because of the extreme heat flowing through the exhaust system. In order to prevent a repeat of this bluing, you need to find out what is causing this heat.

As discussed above, the reasons could include – lean Air-Fuel mixture in the engine, ignition timing is off or there are leaks in the exhaust system.

You need to examine your bike for inspecting these causes. Better take the motorcycle to your mechanic and thoroughly examine the cause.

If the cause of this excess heat is serious, exhaust pipe coloring will be the least of your worries. There might be other potential damages to your motorcycle. So, without hesitating, fix the issue. The coloring of exhaust pipe will be automatically taken care of.

#2. Use Ceramic Coating

If you find that there are no serious problems in your motorcycle, the exhaust pipe material is itself the issue here. The pipe material may not be the most suitable one and the heat flowing through the exhaust is causing it to turn blue.

One solution here is to coat the interior of the exhaust with ceramic. This coated layer will prevent from the metal to get oxidized due to the extreme heat in the exhaust system.

However, ceramic coating is a laborious process and you need to take your motorcycle to a professional here.

#3. Replace The Exhaust Pipe Material

Another solution when the exhaust pipe material is not suitable for the heat releasing in the exhaust system of your motorcycle is to replace the exhaust pipe material itself with a more suitable one.

A description of different materials used as exhaust pipes are given below.

Materials Used As Exhaust Pipes

Every material has its strengths and weaknesses. The selection of the material for exhaust is always a trade off between weight, heat resistance, durability and ease of manufacture.

Here are the most commonly used materials in the exhaust pipes of motorcycles.

Stainless Steel

Stainless is the most commonly used metal in the exhaust pipes owing to its better performance in resisting heat and corrosion when compared to most materials.

However, Stainless Steel does not withstand heat cycles very well. It is more likely to fail at higher temperatures.

Mild Steel

Mild Steel is the least expensive to manufacture. It also performs well to withstand heat cycles. However, the resistance to heat is poor when compared to Stainless Steel.

Given its low cost and high durability, Mild Steel is still popular as an exhaust pipe material.

Ceramic Coated Steel

Ceramic Coated steel is nothing but a ceramic layer added to the interior of a Stainless-Steel exhaust pipe. The Ceramic coating provides additional insulation properties, making the exhaust withstand higher temperatures and more durable.

On the flip side, ceramic coating is difficult to manufacture and as a result are expensive when compared to Stainless Steel and Mild Steel exhausts.

Titanium

Titanium is the most expensive material out of the other alternatives owing to its complex manufacturing process and the intensive labor required.

However, the high cost is compensated with low weight, better resistance to heat and extremely high durability.

Color Of Steel Pipe At Various Degree Temperatures

It is not necessary that the color of your exhaust pipe should only turn blue. Depending the material used for exhaust and the temperature, the exhaust pipe might turn gold, yellow, brown and even red.

For illustrative purpose, here is the table of colors that steel can take at various temperatures.

ColorO CO F
Light Yellow220430
Pale Straw Yellow230445
Dark Straw240465
Yellow Brown250480
Brown Purple270520
Dark Purple285545
Full Blue290555
Dark Blue315600
Greyish Blue330625
Dark Grey427800
Brown Red6001110
Cherry Red7151320
Orange9301705
Yellow10501920
White12002190
Melting15002730

Summing Up

  • The reason why your exhaust pipes turn blue is because of the excessive heat going through the exhaust pipes.
  • The exhaust pipes are designed to withstand heat, however if there is too much heat with soaring temperatures, the exhaust pipe metal starts coloring.
  • The main causes for this excessive heat are:
    1. Lean Air-Fuel mixture in the engine
    2. Ignition timing is off
    3. Leaks in the exhaustion system
    4. Exhaust Pipe material is not right
  • To remove the blue color on the exhaust pipe, you can use products and solutions specifically designed for removal. All you need to do is apply the solution, wait for sometime and clean them. The coloring is removed.
  • However, if you are okay with the blue color on your exhaust pipe, you need not worry. The oxidized layer formed on the surface will do no harm to the motorcycle.
  • To prevent your exhaust pipe from turning blue again, you can take these steps.
    1. Finding the root cause of the heat
    2. Using ceramic coating
    3. Replacing the exhaust pipe material
  • Every material has its strengths and weaknesses. The selection of material for exhaust is always a trade-off between weight, heat resistance, durability and ease of manufacture.
  • The most commonly used materials for exhaust pipes are: Stainless Steel, Mild Steel, Ceramic coated Steel and Titanium.