Exhaust bluing on a motorcycle is annoying for a few riders. And a thing to flaunt for a few other riders.
I definitely fall in the former category.
No matter which category you are in, you should know why there is bluing.
So, why does a motorcycle exhaust pipe turn blue?
Exhaust bluing in a motorcycle is because of the excessive heat on the exhaust pipe. The metal forms an oxidized layer due to the extreme heat, which colors the exhaust pipe blue.
Exhaust overheating is primarily caused by a lean air-fuel mixture. Other causes can be exhaust leaks or incorrect pipe material.
What’s the solution then?
How to fix exhaust pipe bluing?
You can use a metal polish to remove the bluing on the exhaust.
Other fixes include – using an exhaust wrap, powder coating the pipe, or changing the exhaust with a different material.
You can also leave the bluing pipe as it is. There is no harm in it.
Rather, address the exhaust overheating problem.
To know more about exhaust coloring, let’s dig in.
Why do exhaust pipes turn blue?
The reason why motorcycle exhaust pipes turn blue is because of the excessive heat on 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.
What is this bluing then?
The blue 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 the 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 bluing on motorcycle exhaust pipes?
The exhaust pipe turning blue due to extreme heat is not a big problem. But, 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:
- Engine is running lean
- Ignition timing is off
- Leaks in the exhaustion system
- Exhaust Pipe material is not right
Let’s dive deep into each of these causes.
1. Engine is running lean
Lean air-fuel mixture refers to a low proportion of fuel in the engine for the air present.
A 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.
The air has to carry all this heat and flow through the exhaust system.
As a result, the excess heat flowing causes the exhaust pipe to color
(mostly blue) which you are seeing in the form of a blue pipe.
If the 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, the engine has to be ignited much earlier so that the engine can release the 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 exhaust
Any kind of leakage in the exhaust system can also cause extreme heat to flow through the exhaust pipes.
Leaks in the exhaust system are difficult to examine.
To identify the leakage, look for scorch marks along the exhaust. The scorch marks combined with a burning smell around that area are a clear indication of an exhaust leak.
Most commonly the leaks will be in the connections. Try checking the connections first. Mufflers to head pipes, head pipes to exhaust manifolds.
Here is our post on exhaust leak symptoms that can help you confirm if there is a leak.
But exhaust leakage is another way for the exhaust pipe to heat up, form an oxidized layer, and turn blue.
4. Exhaust pipe material is not right
If your motorcycle is new and you are seeing the exhaust pipe bluing within a few days of your purchase, then the material used for the exhaust pipe is not the right fit.
Typically, the most commonly used materials are – stainless steel, mild steel, titanium, and ceramic-coated steel.
To dig deeper. here is our detailed post on exhaust pipe materials.
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 a ceramic coating on 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.
Solutions for exhaust pipe bluing
Here are the few solutions you can go for when your motorcycle exhaust has turned blue.
#1. Use a metal polish
If you don’t like the blue color on your exhaust pipe and wish to remove it, you can use a metal polish.
There are cleaning and polishing products specifically designed to remove the bluing of exhaust pipes.
But a regular chrome polish works just fine as well.
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 it on the 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.
- Apply the solution to the colored region of the 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.
Note: The polish while removes the oxidized layer also causes a rough finish on the metal surface.
So, do not use the product too often on the exhaust pipe.
#2. Use exhaust wrap to cover the bluing
Exhaust wraps come in handy to cover the exhaust bluing.
The wrap overlays and hides the coloring.
Not just the bluing, the exhaust wrap also hides the dents, scratches, and any scorch marks on the pipe.
In addition, they also protect the exhaust pipe from overheating and help in exhaust scavenging.
Overall the exhaust wrap is a good fix for a bluing exhaust.
The only downside is if the water enters the wrap, it will speed up the rusting.
#3. Ceramic coating
The exhaust pipe material on your motorcycle might not be the most suitable one.
The heat flowing through the exhaust is causing it to turn blue.
One solution is to coat the exhaust with ceramic.
This coated layer will prevent the metal from oxidizing due to the extreme heat.
However, ceramic coating is a labor-intensive process and you need to take your motorcycle to a professional here.
#4. Change the exhaust pipe material
Another solution when the exhaust pipe material is not able to withstand heat is to replace the exhaust pipe material itself.
There are different exhaust pipe materials that you can use.
The most common materials for motorcycle exhaust pipes are:
- Stainless steel
- Mild steel
- Titanium
- Ceramic coated steel
In addition, carbon fiber is sometimes used for the exterior and aluminum for the muffler.
Stainless steel is the most common.
If you want the exhaust to withstand heat, titanium exhaust is the best option.
#5. Leave the bluing pipe as it is
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 further damage if left unchecked.
Personally, I leave the bluing as it is. Unless it’s a new motorcycle.
Preventive measures
Okay, you have cleaned the bluing on your exhaust pipe. But you don’t want this situation to repeat.
So, how to prevent exhaust pipe coloring then?
Here are the preventive measures:
- Check carburetor tuning: Lean air-fuel mixture is the primary cause of exhaust overheating. Tune the carb. And set it right.
- Examine spark plugs: Spark plug covered in soot can throw the ignition timing off. Make sure the spark plugs are in good working condition.
- Ensure fuel filter and fuel lines are not clogged: Lean fuel mixture can also be because of restricted fuel flow. Inspect the fuel filter and the fuel lines.
- Check for exhaust leaks: Start with exhaust connections. Mufflers to head pipes, head pipes to exhaust manifolds. Look for scorch marks and a burning smell.
Exhaust pipe coloring at higher temperatures
It is not necessary that the color of your exhaust pipe should only turn blue.
Depending on how the motorcycle exhaust can get, the pipe might turn gold, yellow, brown, and even red.
For illustrative purposes, here is the table of colors that a steel exhaust pipe can take at various temperatures.
| Color | O C | O F |
|---|---|---|
| Light Yellow | 220 | 430 |
| Pale Straw Yellow | 230 | 445 |
| Dark Straw | 240 | 465 |
| Yellow Brown | 250 | 480 |
| Brown Purple | 270 | 520 |
| Dark Purple | 285 | 545 |
| Full Blue | 290 | 555 |
| Dark Blue | 315 | 600 |
| Greyish Blue | 330 | 625 |
| Dark Grey | 427 | 800 |
| Brown Red | 600 | 1110 |
| Cherry Red | 715 | 1320 |
| Orange | 930 | 1705 |
| Yellow | 1050 | 1920 |
| White | 1200 | 2190 |
| Melting | 1500 | 2730 |
Summing up
Here are the things you can do if your exhaust pipe has turned blue:
- Solution 1: Use a metal polish.
- Solution 2: Use exhaust wrap to cover the bluing.
- Solution 3: Apply ceramic coating on the exhaust pipe.
- Solution 4: Change the exhaust pipe material.
- Solution 5: Leave the bluing pipe as it is since bluing is just an oxidized layer.
Irrespective of the solution you go for, you must also address the root cause that’s causing exhaust overheating.
Check for exhaust leaks, carburetor tuning, spark plug condition, clogged fuel lines, and fuel filter.
Before you go…
Here are a few more motorcycle exhaust related posts for you: