Why Is My Motorcycle Smoking? 4 Reasons And How To Fix It


Troubleshooting issues on a motorcycle can sometimes leave us in a guessing game. Though motorcycles are a lot more simple than other vehicles, there are still various reasons and possibilities as to why it’s behaving a certain way.

Seeing excessive smoke coming from your motorcycle can ruin your day very quickly. It’s also one of those issues that you can’t ignore and likely have to address quickly.

Why is my motorcycle smoking? A motorcycle can smoke due to worn out piston rings inside the engine that causes oil to seep up into the combustion chamber. Motorcycle smoking can also be caused by an external engine oil leak that burns from the heat of the engine, poorly grounded wires, as well as newly installed exhaust wraps that haven’t fully cured themselves yet.

I’ve owned over a dozen motorcycles over the last few years and ran into this problem a handful of times. This is what I have learned that causes the issue and how I successfully addressed and fixed it.

Why A Motorcycle Smokes

Any time you see excessive smoke in any situation, no matter where you are, it should be promptly addressed. Smoke is mother nature’s way of warning us that something isn’t quite right.

Having smoke come from your motorcycle isn’t a rare occurrence among these types of machines. In fact, it’s almost pretty common, especially with older motorcycles. But it can be scary when you see it and you’ll probably want to fix it quickly because it’s also pretty embarrassing.

If your motorcycle is smoking excessively from the exhaust, the first and most common reason, especially among older motorcycles, is due to worn out piston rings. Piston rings seal two compartments of your engine away from each other. It seals the top half of the cylinder, which is the combustion chamber, and it seals the bottom half which is the crankcase.

Your crankcase is full of oil and that oil is squirting and splashing up against the bottom of the piston and against the other components in your engine to keep them lubricated.

But you don’t want oil getting past the piston rings up into the combustion chamber because you want the gas combusting instead of the oil. This will quickly use up your oil which could possibly overheat your engine and will cause excessive smoke to come out of your exhaust. This is usually caused by normal wear and tear and regular usage of the motorcycle.

The second most common reason a motorcycle will smoke is if you have an oil leak and oil is getting onto the outside of the engine and then burning off from the heat. This will cause smoke that comes directly from the engine itself.

This should be evident after you stop riding if you have any oil on your engine at all. Look in between the fins of the engine; usually the cylinder comes in separate pieces so you will be able to see the lines around your engine as well as any oil leaks coming from those lines/seals.

If you have smoke coming from somewhere else on your motorcycle that’s not from exhaust or the engine, you could have wires burning. This is the most dangerous type of smoke because it can ultimately start an electrical fire.

I once had a motorcycle where the wiring caught on fire because a positive wire accidentally touched the metal frame and there was no fuse on that line. This type of burning will often be accompanied by the smell of burning rubber. Look over your wiring and wiring harness for any burns, scorch marks, or melted plastic. This should be promptly fixed before starting your motorcycle.

Another reason a motorcycle may smoke could be due to new exhaust wrap on the exhaust pipes. This is a fiberglass based product that’s wrapped around exhaust pipes for both looks and as a safety guard to prevent burnt feet and ankles.

After this is installed, the fiberglass burns off and hardens as you ride. These will smoke a bit and smell unpleasant the first few hours after you ride your motorcycle. This is normal if you or a shop recently installed these.

How To Tell What The Issue Is By The Type And Smell Of The Smoke

In some cases it can be obvious where the smoke from your motorcycle is coming from. It can be difficult in other cases because smoke may seem like it’s coming from one place but could really be from a different source.

If it’s hard to visually see, your motorcycle can help you figure out exactly where the smoke is coming from by what color the smoke is and what the smoke smells like. Obviously smoke will have a general smell, but these issues previously described will each have an additional distinct smell to them.

If the smoking is caused from failing piston rings, there will be an excessive amount of smoke coming out of the end of your exhaust pipes. This will usually be a white smoke with a blue-ish tint to it. And it will smell like burning oil which is different from the normal exhaust smell.

When you have an external oil leak that’s burning from the heat of your engine, you will again get a white smoke with a blue-ish tint to it accompanied by the smell of burning oil. These first two should be easily distinguishable since the engine and the exhaust pipe are generally a foot or so apart from each other.

Smoke that is coming from the wires of your motorcycle is also very distinguishable. This will emit a very dark, almost black smoke and will be accompanied by the smell of burning rubber (because the rubber casing around the wires are burning).

If the smoking is caused by new exhaust wraps, you will notice a white smoke, almost looking like steam, coming from the entire length of the exhaust wrap. This emits the smell of burning fiberglass which is quite unpleasant to smell.

How To Fix Smoking Issues

Once you’ve figure out the source of the smoking on your motorcycle, you’ll probably be left wondering how to fix it. A lot of these issues can be fixed yourself if you have a set of basic tools and are willing to do a little bit of research. Click hereOpens in a new tab. to see my list of recommended tools.

It can be a little tricky when you’re dealing with failing piston rings inside your engine. You can start with doing a compression test on the engine. This tests the pressure inside each cylinder separately and if the pressure is low in one or more cylinder that likely means you need to replace the piston ring. Unless you’ve done this before, this is the one fix I recommend you take into a shop and have them do.

If you suspect your motorcycle smoking issue is coming from an engine oil leak, you either need to change the gaskets and/or tighten the bolts. It is possible to change the gaskets yourself, but you’ll need a little experience to accomplish this. For further information about how to change the gaskets on your motorcycle engine, see my other article hereOpens in a new tab..

If you are going to tighten the bolts on your engine, look in your owner’s manual (or you can probably look it up online) and tighten the bolts up to the proper torque specs. Or you can simply take it into a mechanic and have them retorque the engine for you.

It’s important that you don’t free-hand the tightening of the bolts on your engine. This can either lead to further oil leaks or ultimately crack parts of the engine from tightening bolts too tightly. I’ve made this mistake before and it’s not worth it. Do your research first.

If your wiring is your issue, inspect all the wires on your motorcycle to determine which wire is the problem. Immediately replace that wire and be sure to splice it properly to prevent problems in the future. Also ensure that particular wire is correctly grounded and that it is protected by a fuse. Also make sure it won’t rub up against anything such as the front or back tire.

Smoke coming from exhaust wraps should resolve itself after a few hours of riding. If you’ve noticed it is not stopping, you may need to rewrap the exhaust pipes and be sure to get them wet first and install them tightly.

How Much Smoke Is Considered Normal?

There may be some out there that questions if their motorcycle even has an issue at all and if the amount of smoke their motorcycle is emitting is normal. This can help you calibrate further issues on your motorcycle.

It is normal for some smoke to come out of the end of the exhaust pipes. Motorcycles don’t have a catalytic converter that converts the exhaust fumes into non-noxious gases. This will in turn cause a little more smoke to come out compared to other vehicles.

With that being said, there should not be an excessive amount of smoke coming out of the exhaust. Only enough to notice it a little bit. The smoke should also be faint white. On colder months the exhaust will be much more noticeable because of the cold temperatures. Aside from this, there should be no other smoke coming from any other parts of your motorcycle.

Related Question

Why is my motorcycle idling high? A motorcycle idles high when it is getting too much of an air and fuel mixture in a low speed or neutral position. This is usually caused by the idle screw on the carburetor being out of adjustment, an out of place throttle handle screw, a bad carburetor throttle spring, or a sticky throttle or throttle cable. Click hereOpens in a new tab. to see my article for more information.

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