Motorcycle Exhaust Glowing Red? Why it’s happening and how to prevent it

If you notice your motorcycle’s exhaust glowing red, fret not. This is a fairly common issue that almost every motorcycle rider has to deal with at some point. 

What causes your motorcycle’s exhaust to glow red and the intensity with which it glows depend on various factors. In most cases, the red glow will be localized around your motorcycle exhaust’s header pipes. However, it may extend further down as well. 

So what exactly causes your motorcycle’s exhaust to glow red? And more importantly, what can you do to fix it before it causes some significant damage to the engine?

Is my exhaust evolving???

Your exhaust isn’t evolving into anything. What you see is the exhaust gasses heating the metal to the point where it is visibly glowing. The glow itself can range from a dark red that is hard to make out to a bright orange that is hard to miss. 

Now motorcycle exhausts are made of materials specially designed to resist the highest of temperatures. But the same cannot be said for some sensitive engine components. If you ignore a glowing red exhaust long enough, it could cause severe damage to your motorcycle’s engine. 

But before we figure out how to treat the problem, we must first diagnose it. Here are a few possible reasons for your motorcycle’s exhaust glowing red. 

1- The engine is running too lean

If your motorcycle’s exhaust gasses are becoming hot enough to make the exhaust glow, it’s usually a sign that the engine is running too lean. 

‘Running lean’ refers to when an engine has an overabundance of air without enough fuel. The resulting air-fuel mixture can lead to a furnace effect, and the glow is a visible symptom. 

But how can you be sure that the engine is running too lean? Well, there are a couple things you can try. 

First, ride the bike for a few minutes, rolling on and off the throttle. If, when you roll off the throttle, the bike starts backfiring, it is a good indicator that the engine is running too lean. 

A little bit of popping or crackling is normal, and nothing you should lose sleep over. But if it is really noticeable, the engine is probably running too lean. 

Another dead ringer for an engine running too lean is ‘idle hang.’ This is when you roll off the throttle, and the engine revs do not drop at once. Instead, they stay at higher RPMs for a while before dropping down. 

If you want to be absolutely sure your bike is running lean, check the spark plug. Remove the spark plug and clean it properly. 

Reinstall the plug and go for a short ride. Now, you are trying to put some extra load on the bike, so feel free to go full throttle if possible. Once that’s done, remove the spark plug again. 

Typically, the plug should range from brown to gray and be slightly moist with engine oil or gasoline. If you notice a white residue on the very tip of the plug and no engine oil or gasoline on it, your bike is running too lean. In extreme cases, the end of the plug may even start melting!

So now that you’ve determined that the bike is running too lean, what can you do to fix it? Well, the first thing you should try is cleaning the carburetor. A clogged-up pilot jet could also be the culprit. Lastly, cracked vacuum lines could also cause the bike to run lean, so definitely check those. 

2- The exhaust valves are not working properly

If the bike isn’t running lean, the exhaust valves may be to blame. These valves may get caked with carbon residue over time, preventing them from sealing properly. This could let the hot gasses and possibly even flames from the engine escape and cause the exhaust to become too hot. 

And unfortunately, an exhaust valve check isn’t as easy to do as figuring out if your bike is running lean or not. Unless you’re already comfortable wrenching on your bike, professional help is recommended. 

3- Your motorcycle’s exhaust may be leaking

If the exhaust gasses are leaking out before they are ejected, the exhaust system could become too hot and start glowing. To check if the exhaust is leaking or not, look for damaged gaskets, loose-fitting clamps, or even cracks in the metal. 

4- Restricted exhaust flow

If something prevents the exhaust gasses from exiting the engine, they could build up in the exhaust pipes and cause the metal to start heating up. The glowing effect will usually follow close behind. 

A number of things can restrict the flow of exhaust gasses. Some dirt or road debris may have found its way into the exhaust. We have had to deal with enough chewed-up electrical wires to know that pests such as mice love checking out motorcycles and cars from the inside when they are stored for the winter. Heck, you could have been the victim of some sick-minded individual’s idea of a prank. 

Thoroughly inspect the inside of the muffler to see what’s causing the issue. And be prepared to take apart the whole exhaust to clear away any blockages. 


So that’s just a couple of the possible reasons your motorcycle’s exhaust is glowing red. But the truth is that it could be none of the above. If you are still scratching your head trying to figure it out, perhaps a trip to the mechanic will do both you and your bike some good.\

Hugo Alais

Hi, I'm Hugo, I'm a motorcycle enthusiast who’s been riding for the last 10 years. I'm passionate about all things motorcycles and started Bikes Future to help other riders make the right motorcycle moves. I ride a white Kawasaki Ninja 400. You can find out more about me and my experience with motorcycling here.