White smoke coming from your motorcycle exhaust is harmless most of the time. Most likely it’s the water vapor condensed in the exhaust.
But some white smoke is concerning.
If the white smoke is caused by condensed water vapor, there is nothing to worry about. But if the white smoke is due to a coolant or engine oil leak then it needs to be taken care of.
In this post, we will deep dive into these causes and subsequently the solutions in detail.
Reasons for white smoke
Here are the main reasons for white smoke coming from motorcycle exhaust.
#1: Water vapor in the exhaust
Water vapor in the exhaust is the most common reason for white smoke.
The water vapor is usually condensed. And is accumulated along the insides of the exhaust pipe.
So when you start the motorcycle, the heated exhaust gases take these condensed water vapor out.
White smoke coming from the exhaust.
But only for a short time.
The white smoke due to water vapor only lasts for a minute after you start the motorcycle. Post that, the motorcycle runs normally with clean exhaust gases.
That’s why white smoke for a short period is completely harmless.
It’s just condensed moisture getting out of the exhaust system.
You don’t have to worry about such short-lasting white smoke on your bikes.
How to fix:
White smoke due to water vapor is harmless.
The white smoke won’t last long and after a minute a two, the exhaust will give out clean gases.
So there is nothing to worry about. And nothing to fix here.
#2: Coolant is leaking
Coolant leak is the second common cause for white smoke from motorcycle exhaust.
If the white smoke persists for longer periods on your motorcycle, then water vapor is not the reason.
That brings us to the second possible culprit – coolant.
Now, if your motorcycle is not liquid-cooled, then there is no coolant in there. In that case, you can skip this section and head to the next possible cause.
But if your motorcycle is liquid-cooled, you need to check the coolant levels.
Checking the coolant levels on your motorcycle:
- Remove the coolant reservoir tank cap and check the levels. The coolant level must be between the high and low markings.
- Remove the radiator cap and check the levels. The coolant must be filled to the brim.
If the coolant level is not right in either the radiator or the reservoir tank, then there is a coolant leak.
(Unless of course you haven’t changed the coolant for years).
But low coolant levels are a good indicator that the coolant is leaking.
You can confirm again by checking the engine oil quality as well. The engine oil color and texture can tell if the coolant is mixing with the oil.
If the engine oil is frothy with white or green tinges, then the coolant is definitely leaking.
The leaking coolant is what is causing white smoke from your motorcycle exhaust.
How to fix:
The coolant leak requires close inspection. Starting from the radiator to the engine combustion chamber.
Most likely, the head gasket needs to be replaced.
A thorough inspection and solution are detailed in the solutions for the white smoke section below.
#3: Motorcycle is burning engine oil
Another cause for the white smoke from the exhaust is if the motorcycle is burning engine oil.
Few riders say, engine oil burning results in gray smoke. And white smoke is coolant burning only.
While theoretically, it might be true. But I am not fully on board with it.
I can’t really differentiate white smoke from gray smoke.
Black smoke? Sure. I can identify that.
But any lighter shades of gray, I can’t tell the difference between the gray smoke and the white smoke.
Look, it’s tough.
And there were times when there was white smoke from the exhaust and overfilled engine oil was the culprit. Maybe it was gray smoke and I couldn’t tell. But for me, it was white smoke.
So instead of debating the smoke color, it’s better to check whether the engine oil is indeed burning.
First, check the engine oil level.
If the motorcycle is burning the oil, the oil levels must be low. The oil dipstick should easily tell you that. If the level is below the low mark, the engine oil is depleting.
Second, to confirm, check the oil quality.
If the oil has a burnt smell, then the engine is burning the oil.
To inspect, take out the dipstick and apply the oil to your finger or tissue paper.
Smell the oil. You will get a burnt smell if the oil is leaking into the engine.
That confirms the engine oil causing the white smoke from the exhaust.
How to fix:
To address burning oil, the oil leak needs to be fixed.
This is easier said than done of course.
The oil leak can be due to valves, gaskets, or damaged piston rings.
Short-term fixes can include additives, engine flushing, and using high-quality oil.
Detailed solutions are discussed in detail in the next section.
Solutions and Preventive Measures
Now that we know the causes, here are the solutions for white smoke coming out from your motorcycle exhaust:
- For water vapor – do nothing: Condensed water vapor induced white smoke is harmless. The white smoke from the exhaust only lasts for a minute or two. There is nothing wrong here and you don’t need any fix.
- Use sealing additives: This is a short-term fix. Coolant and oil leaks need a thorough inspection. And can be labor intensive. For a quick fix, you can try Teflon-based sealing additives for the oil and/or coolant to seal the path and prevent leaks.
- Go for engine flushing: Engine flushing deep cleans the engine. It will remove contaminants and help restore the engine to its peak condition. This helps, to a large extent, in containing the leakages.
- Use high-quality oil and coolant: If poor-quality coolant or oil is the issue, change them. Use a multigrade oil, synthetic if the manufacturer recommends. For coolant, avoid OAT and HOAT since they aren’t usually good for motorcycles.
- Seal the valves: This is a long-term fix but a difficult one. Go for it only if the leakage is too high. You need to take your motorcycle to the dealer or a service shop for this.
- Change the head gasket: If the coolant leak is too high, changing the head gasket will most likely address it. Confirm if the leak is via the head gasket before changing it. This is labor intensive and you might have to take it to a service shop.
- Replace piston rings: Let’s hope things won’t come to this. But if the engine is old and weak, it might come to this. Replacing piston rings is labor-intensive and costly as hell. Go for piston ring replacement only as the last resort.
Is white smoke from motorcycle exhaust bad?
If the white smoke from motorcycle exhaust last for only a short period, then it’s not bad. But if the white smoke persists longer then it is a bad thing.
White smoke lasting only a minute or two after you start the motorcycle is because of water vapor condensed within the exhaust.
Once the water vapor is pushed out the exhaust, the white smoke stops by itself.
But, on the other hand, if the white smoke keeps on coming from the exhaust, it is a serious concern.
Such white smoke is either due to the coolant leak or the engine oil leaking in the engine.
In either case, the leask must be addressed.
Can fuel cause white smoke?
If the fuel contains water particles in it, then the fuel can also cause white smoke.
The water within the fuel burns along with the fuel to form white exhaust gases.
In such cases, it is better to change the fuel.
While a small amount of water in fuel is harmless, it’s still not recommended to ride on.
So change the fuel if it has water particles in it and is causing white smoke from the exhaust.
Can low oil cause white smoke?
Low engine oil levels do NOT cause white smoke from the exhaust.
Rather, high oil levels can cause white smoke.
The excess oil can flow into the engine and burn there. The burnt oil often results in bluish-white smoke.
While low engine oil levels do not cause white smoke, they cause other problems. Most serious of them include overheating, worn-out combustion cylinders, and engine seizures.
So, both low and high engine oil levels are not good for the motorcycle.