It can be an incredible experience, ripping around curves when suddenly you smell burning to waft up from your motorcycle.
It could be issues with your gearbox, brakes, exhaust, or even your engine, making a burning smell an important reason to pull your motorcycle over and troubleshoot.
We’ve come to speed up your troubleshooting process by listing the 9 most likely reasons why a burning smell could come from your motorcycle.
Table of Contents
1. Foreign Object Melting in Exhaust Pipe
Multiple consumer and technician reports published in online forums described burning smells occurring while riding a motorcycle resulting from plastic children’s toys lodged in the tailpipe, causing exhaust issues, and then melting down into burning plastic puddles and fumes.
- If a plastic item like a children’s toy gets shoved into your exhaust, it may be shot out at startup.
- If the force of your initial ignition exhaust isn’t enough to push the object out of your tailpipe, it may melt down while you’re riding, causing a burning smell.
- If the foreign item is large enough, the burning melted plastic may clog your pipe, causing exhaust failures, including but not limited to a pipe rupture.
If the burning smell you’re experiencing while riding your motorcycle comes from your exhaust pipe and has a plastic scent to it, inspect your tailpipes for clogs.
2. Fuel Leak Causing Burning Fuel Smell
If the burning smell of your motorcycle is generating odors like fuel, fuel may be the root cause of the burning gas smell. Fuel leaks begin in either the tank, fuel lines, carb, or injection system.
- If the motorcycle is overfilled, the unneeded fuel is sprayed out of an overflow hose onto the ground.
- Sometimes, the draining fuel splashes onto the tailpipe, which is still hot from riding.
- In other situations, fuel leaks from where the valves and hoses hook up to your bike’s fuel tank underneath it.
- Contact with the hot tailpipe can cause a burnt fuel odor.
- Finally, an improper air-fuel ratio rich in fuel can overflow your combustion chamber with fuel, forcing liquid fuel into your exhaust pipes where it will combust, causing loud pops and the smell of burning gas.
Petrol fuel is combustible, meaning fuel leaks should be resolved before starting and riding the motorcycle. Overfilling your tank is one thing, but if you suspect a fuel leak is why your bike smells like burning gas, repair the leak immediately.
3. Faulty Head Gasket
While head gaskets generally don’t fail on a well-maintained and responsibly stored and ridden motorcycle, they can cause strong burning odors when it does.
- If a blown head gasket is the reason your motorcycle is generating a burning smell, you’ll likely notice unusually thick white exhaust smoke.
- The most common cause of a failing head gasket is engine wear, either due to overworking the motor by riding hard or improper storage and maintenance neglect.
- The overworked engine gets hot sporadically, causing the motor block metal to expand at inconsistent rates.
- The expanding metal creates a gap the head gasket stretches to attempt to seal.
- The overworked head gasket inevitably blows out in the process.
In addition to the white exhaust steam and a burning smell, a blown head gasket causes engine overheating and oil and coolant leaks outside the machine.
On liquid-cooled motorcycles, a blown head gasket also causes your oil to be contaminated by a milky sludge, as coolant is leaking into your oil reservoir.
4. Worn Exhaust Pipes or Headers
Worn pipes and headers can develop leaks and cracks that let exhaust and combustion fumes escape your exhaust system while riding. These fumes are associated with fuel combustion and will smell like burning fuel.
Even the highest-grade motorcycle exhaust system wears out eventually, if not from the exhaust heat, road grime, street salts, rust, and corrosion caused by moisture and UV rays.
- Your exhaust system is a critical part of the process that generates the force required to thrust your motorcycle forward and, therefore, needs to be inspected during routine service intervals.
- If cracks, holes, or leaks develop in your exhaust headers or pipes, the escaping burning fumes aren’t visible, making a small leak hard to detect.
- You can diagnose if an exhaust leak is a culprit behind the bike’s burning smell by looking for other symptoms, like popping sounds from the pipes or headers while the bike is running.
- If you experience popping sounds and smell exhaust vapor, hover a piece of paper over the exhaust pipe and up to the header.
- If the piece of paper starts to flap like it’s in front of a fan, you’ve found the location of the exhaust leak causing the burnt fuel odor.
Note: The poignant burning exhaust scent referenced in this section is much stronger than the typical smoke smell from your exhaust during everyday riding. We’re referring to a distinct and consistent pungent burning fuel smell escaping from your exhaust, accompanied by popping and strange exhaust sounds.
5. Worn Piston Rings Causing Burning Smoke
If your motorcycle’s piston rings are worn out, your tailpipes will produce a thick cloud of dark black smoke, much different from the standard exhaust, and the smoke itself will smell burnt.
- Once the piston rings are shot, they fail to seal correctly.
- The unsteady piston ring allows oil to pass through where it shouldn’t.
- Eventually, the oil leaks into your combustion chamber, where it burns up during the fuel combustion.
- The vaporized oil escapes through the exhaust system as a dark cloud of smoke that reeks of burning fat.
If blown-out piston rings make your motorcycle smell like burning oil, your oil level will decrease rapidly. Replace the worn piston ring before riding the bike.
6. Oil Reservoir Is Overfilled
Overfilling the oil levels on your motorcycle forces the excess oil into the engine, which burns up and is released as a scorched black smoke of vaporized oil, mimicking the symptoms of a worn piston ring.
Additionally, exceeding the limits of your oil reservoir’s max fill level can cause oil seals to blow, causing even more oil leaks that lead to burning oil smells.
We’ll cover oil leaks more extensively in a later section; overfilling your motorcycle’s oil can lead to crankshaft pressurization and oil clogs in your air intake, which risk engine damage that generates the smells of seized metal and burning fat.
7. Exhaust Packing Fibers Burned Up in Tailpipe
If you or a mechanic incorrectly installed an exhaust silencer box, or if the package isn’t compatible with your exhaust, the internal quieting fibers can burn up, vaporize, and blow out of the pipes in thick, scorched smoke.
- Some motorcycles equip a silencer box that quiets the exhaust.
- Simply put, the box is full of packing fibers that absorb the soundwaves before they can exit the pipe and produce a loud noise.
- The fibers are meant to vaporize over time, but if installed improperly or if the box doesn’t correspond with the exhaust system, the fibers will burn up, producing strange exhaust fumes and odors.
Suppose the box isn’t fitted with replacement packing fiber or installed correctly. In that case, your motorcycle will continue to produce unconventionally strong exhaust fumes, and your motorcycle’s performance, torque, and horsepower will all dip.
8. Leaking Oil Burning Up in the Bike’s Motor
One of the most common reasons a motorcycle makes a burning smell while riding is because of a stripped filler cap drain plug, a worn oil filter seal, or a blown oil seal between the motor block and the oil pan.
All of these allow oil to leak into the engine and burn up, resulting in the smell of burnt fat.
- In some situations, the oil gets into the air or fuel system and eventually into the combustion chamber, where it’s burnt up along with the fuel.
- In other cases, the internal engine heat in spaces oil isn’t meant to flow is enough to heat the oil past its flash point, causing it to burn inside the engine.
- Finally, external oil leaks can cause oil to drip or splash onto the exhaust pipe and smell like grilled fat.
Oil leaks and hot oil can cause engine overheating and increased friction between machine parts. Therefore, any oil leak resulting in a burnt odor should be reified before riding.
9. Burning Brake Pads or Seized Brake Caliper
Burning smells on a motorcycle might be coming from your brakes; the pads may be worn and need to be replaced. Or it may be new brake pads wearing in.
If the pads are fresh and the burning rubber smell persists for longer than a few days, the brake calipers may be seized, or a brake hose is pinched.
- As fresh brake pads wear down, they smell like burning plastic or rubber as their outer layer rubs off against the disc for the first few rides.
- If the burning smell from your motorcycle wheels persists, it may be that one of your calipers is seized, forcing the pad to rub against the rotors even when you’re not applying your bike’s brakes.
- If your brake lines are jammed, clogged, pinched, or corroded, it allows pressure into the brake caliper, which can cause the same symptoms as a seized caliper, including forcing the pad against the rotor and generating a burning plastic smell.
If the brake pads are new, give them a few days and see if the odor stops. Also, ensure you’re not overworking your brakes and burning the pads by pressing the levers too hard while the bike is in motion.
If the pads are good and rider input isn’t to blame, see if your wheel is dragging like you’re lightly pressing the brake levers even when you’re not.
If so, you could have a seized brake caliper or a pinched brake line.