Is A Glowing Red Head Pipe Okay?

Is a red-hot glowing head pipe on your 4-stroke dirt bike “Okay”? No. Is it “normal?” Yes. Is there a way to fix it? Yes, there’s more than one possible solution, although there is one that stands out the most.

If the head-pipe is red, that means the engine is getting too hot and needs more cooling. You may not need any parts to fix this though; let me explain…

dirt bike head pipe glowing red hot
Head Pipe Glowing Red Hot

Dirt bikes that most commonly have a glowing red pipe problem

Basically any 4 stroke dirt bike can have this issue, but there’s certain dirt bike models that have a frequent problem with the exhaust pipe glowing red.

  • Suzuki RMZ250
  • Honda CRF450R
  • Yamaha YZ250F
  • Kawasaki KLX230R

What Causes A Dirt Bike Head Pipe To Glow Red?

The most common causes of a dirt bike head pipe glowing red are:

  • Improper jetting
  • EFI not tuned correctly
  • Idling too long
  • Dirty carb
  • Engine is not getting properly cooled

Jetting too hot

If your dirt bike has a carburetor, then some proper jet tuning can make a huge difference in how your bike runs. If everything is working well, but the jetting is too rich or too lean, then your dirt bike may be: hard to start, have poor throttle response, overheat faster, be less reliable, and more.

Jetting that is too lean will cause the engine to run hot because it’s not getting enough fuel to properly cool it.

Exhaust change without EFI tuning?

Does your 4 stroke dirt bike have fuel injection? Making an exhaust, or even a modification to the engine or intake will make it run differently. The EFI on most dirt bikes is an open-loop system. This means it only takes account of the air temp/humidity.

What’s the result?

The system doesn’t know if it’s running the stock exhaust or no exhaust at all, which will greatly affect the air-fuel mixture. It only adjusts the fuel mixture when the climate you’re riding in changes.

So, if your 4 stroke is running hot after an exhaust system change (even just a slip-on), there’s a good chance that you need to get the EFI tuned. This might be a new ECU and controller, just the controller, or maybe your specific bike has an app available to tune it with WI-FI.


How long are you letting it idle?

There are two ways a 4-stroke dirt bike “cools”. Both of them require riding the bike, so don’t think you can stop and wait to let it cool down. In fact, you want to do just the opposite. First of all, riding the bike gives it air-flow through the radiators (If it’s liquid-cooled), naturally.

So if you’re standing still, the cooling system isn’t going to do a whole lot. This is the most common issue for beginning riders and trail riders that do tight single track. The more you stay moving the better.

Head pipe getting red hot from sitting idling

Gas Cools It

The next possible solution is similar to the first, but in a different way. You now know that riding at higher speeds will reduce the chances of overheating because radiators need air-flow. Gas is the other cooling part. The more gas going through the cylinder head and combustion chamber, the more it will keep it cool, to an extent.

Like before, if you’re sitting with the bike idling, it’s not getting enough gas to burn and keep cool, even if your jetting may be correct (although, lean jetting can also cause overheating problems).

A lower-performance trail bike should not have a glowing head pipe from idling. If that is the case, then the jetting is too lean, or the EFI is too lean and needs to be richer. This can be done with a bigger pilot jet for a carburetor, or richening the EFI system with a fuel programmer.

Valves wear out quicker with heat

It’s not necessarily the entire engine that overheats from a lack of gas. It’s the valves that start to heat up and eventually burn out. If you’ve been around 4-stroke motocross bikes at all, you have probably heard the term “Burnt a valve.”

Well, this is one of the main reasons why it happens. The valves just get too hot too many times, causing them to burn up the edge and lose all compression. It’s better than dropping a valve, but still can be a costly repair.

How to make your valves last longer

Properly warming up your dirt bike is part of it, which is why I never let my four-strokes idle for very long when I first start them up. How do I know this, you ask? Well, I know of many people that have burnt valves more often than usual, and it wasn’t coincidence. No, it was because they putt around on their bikes.

Not only does riding your bike harder and faster give it more air to cool it down, but it also gives it more gas to keep the valves cool, increasing longevity. You will also have more fun riding faster because you’re passing your buddies that are cruising along.

All in all, a 4 stroke motocross bike is made for one thing; to be raced, and raced to its potential. You don’t have to out-ride yourself, and I suggest you don’t. But, the more speed you can get, the better off your dirt bike will be. Quite the contrast compared to most other things, huh?

Dirt bike running hot after sitting in storage for months?

Did you just pull your bike out and now it’s running hot with the head pipe glowing red. You haven’t changed anything since you rode a few months (or possibly a few weeks) ago, so what’s causing it?

If it’s carbureted, then it’s most likely due to it being dirty. The jets and passages are so small that it doesn’t take much of a spec or gas breaking down to gum up and block it. This changes the air-fuel mixture because less gas is getting through the partially blocked passage. Less gas = lean and running hotter.

A quick draining of the float bowl may get sediment that settled out, but a carb that’s been sitting for a while may need a full and proper cleaning.

Free ways to prevent overheating

Want to learn how to keep your dirt bike running cool? These tips are Free to do and will help prevent a catastrophic failure that could leave you stranded in the middle of nowhere. Click here to learn how.


Kelley Fager

I help newer riders learn to safely ride with confidence by teaching basic techniques in a way that's easy to understand. Learn To Ride With Control Here

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