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8 DEADLY Signs Your Dirt Bike Is Overheating [& Why]

Is your 2 stroke or 4 stroke dirt bike overheating but you’re not quite sure why? Does it lose power or have coolant coming out of the overflow hose?

In this article, you’ll learn the most common reasons why your dirt bike is overheating, whether it’s okay or not, and how to properly fix it with multiple solutions, whether it’s a serious problem or not.

What Does Overheating A Dirt Bike Mean?

A proper operating temperature for a stroke dirt bike is between 180 and 220 degrees Fahrenheit. Temperatures hotter than that means that the engine is overheating and damage will happen sooner than later.

What kind of damage can overheating cause in a 2t dirt bike?

Overheating may not cause any damage to your dirt bike, but it really depends on how hot it actually got and for how long. For example, if the engine gets too hot for too long, the piston can melt and basically weld itself to the cylinder wall, leaving you with a seized engine that will be difficult to remove.

Just realize that the longer you let your engine run hot, the more likely you will damage it. It doesn’t take long – a couple of minutes is all it can take to ruin your top end or worse.

Even if it doesn’t seize, an overheated 2 stroke or 4 stroke engine can cause the cylinder head to warp (the gasket surface isn’t perfectly flat anymore) and result in blown head gaskets until it’s fixed or replaced.

How To Tell If A Dirt Bike Is Overheating

The most common signs that a 4 stroke dirt bike is overheating are:

  • Coolant coming out of the overflow
  • Bike is steaming
  • Coolant is burning (smells sweet)
  • Clutch dragging
  • Red hot head pipe
  • Loss of power
  • Oil Leaking from seals
  • Cylinder/engine case is hotter than normal
  • Engine locked up and won’t turn over

Here are the most common symptoms of a 2 stroke overheating:

  • Coolant coming out of the overflow
  • Bike is steaming
  • Coolant is burning (smells sweet)
  • Clutch dragging
  • Loss of power
  • Oil Leaking from seals
  • Cylinder/engine case is hotter than normal
  • Engine locked up and won’t turn over

There are different reasons why your dirt bike may be overheating – Some of them are because of a problem with your bike, but it may just be an issue that can be remedied with a simple fix.

The Most Common Reasons Why Your 4 Stroke Dirt Bike Is Overheating:

  • Low coolant
  • Bad radiator cap
  • Blown head gasket
  • Bad water pump
  • Jetting is too lean
  • Riding Too Slow

Before you do anything, there is one thing you should check that some riders choose to ignore. Coolant flows through the engine to keep your bike running ‘cool’. If there’s little to no fluid, it’s just going to overheat.

Low Coolant?

Water or coolant circulates through the radiators and engine to keep the engine cool, so if there’s little to no coolant, then it can’t properly keep the engine cool. This issue is super easy to prevent, but it’s also easy to forget or neglect.

Before every ride, pop the cap off the radiator to check and make sure it’s full of coolant. Just by doing this, you can prevent an engine rebuild that costs $1500 or more for parts, and that’s not including labor to repair it!

Coolant Leaking Out Overflow Tube 8 DEADLY Signs Your Dirt Bike Is Overheating [& Why]
Low Coolant

Coolant is low after every ride?

On the other hand, if you keep having to fill the radiator because the coolant level is down after every ride, then you have problems. There is a leak somewhere, and you’ll have to take stuff apart to find it.

It will often be a blown gasket (base, head, or water pump), a hole in the radiator, or a radiator hose that’s leaking or has a loose clamp.

Coolant Coming Out Of The Overflow?

Your dirt bike may be losing coolant out of the overflow for a few reasons. As mentioned above, a blown head gasket is a common sign of coolant coming out of the overflow hose.

A bad or leaking radiator cap can allow coolant to leak by, or the engine will simply get too hot and boil it out.
Here are some common signs that your radiator cap is bad:

  • The coolant level is down after every ride
  • Leaking coolant out the overflow even if it’s not overheating
  • Coolant reservoir tank is overflowing (if your dirt bike has one)

Instead of waiting until this happens when riding, you can simply add a radiator cap with a temp sensor (Amazon) on it. That way you can quickly check it while riding to see if the coolant is getting too hot.

Did You Blow A Gasket??

That brings us to the next possible culprit. A worn or torn gasket will allow coolant to seep through, reducing cooling, and very possibly causing damage.

The Water Pump

The least damaging can be the water pump seal/gasket. If you’re lucky, it will just dribble out somewhere around the impeller cover and onto the ground. It can also mix with the tranny oil, causing it to corrode and eventually seize. If that is the problem, it’s best to replace it right away.

The Head Gasket

A blown head gasket can be a cheap fix, but it could also cause an engine malfunction. If you’re running your bike with a bad head gasket, it’s probably burning coolant, which will show up as white smoke out the exhaust.

Cyl. Head 1 edited 8 DEADLY Signs Your Dirt Bike Is Overheating [& Why]
Blown head gasket from CR125

Hopefully Not A Base Gasket

A faulty base gasket is usually going to be worse. Coolant will leak into the transmission, contaminating the oil. This will eventually cause it to fail, or the piston/cylinder will overheat and seize due to the lack of coolant in the radiators. It can also happen in a matter of hours or even minutes.

Inspecting Can Save You Money

This is why it’s always a good idea to take the top-end of an engine off (if it’s a used bike you bought) to see if anything needs replacing, or if something was put in wrong by the previous owner (happens WAY too often, so don’t ever think it won’t happen to you!).

Lean Jetting Will Burn Your Engine Down

Tuning a dirt bike carb to find the right jetting is important for so many reasons. A finely tuned carb will provide better power, throttle response, fuel mileage, and reliability.

Jetting that is too rich will cause your dirt bike to sputter, bog, and run poorly. It will also leave more unburnt fuel deposits (the crusty black stuff) on the piston, exhaust chamber, ports, as well as the inside of the exhaust system.

A lean running engine doesn’t have enough to burn, so it starts burning the metal around it because it’s a hotter combustion. Leaving the jetting too lean for too long will overheat and burn the piston and/or valves down.

Radiators Need Air To Cool As Well…

The other common factor of overheating is not one that everyone realizes – water isn’t the only thing that keeps a liquid-cooled bike cool. Air is still needed to flow past the radiators to keep the radiator temps down.

Dirt bike overheating when idling?

So, if there’s no airflow, then there is little cooling. Simply put, if you’re idling or putting around a lot, your bike is going to start overheating.

Not only does it get hot from little airflow, but the little amount of gas going through the engine also causes it to get too hot. The gas actually cools the intake and exhaust valves as it passes by, so 4-stroke motocross bikes need to be ridden at moderate speeds every so often in order to prevent overheating.

Why 4 stroke valves burn up

This is one of the reasons why valves burn up, so don’t let your bike sit and idle for very long while waiting for it to warm up.

How to properly fix your dirt bike that’s overheating

There are a few ways to fix these problems. If it’s a gasket, then pretty much the only thing to do is replace it. Although if the gasket surface, such as the cylinder or head is warped, then it needs to be resurfaced in order to prevent the same problem.

The benefits of proper jetting

Improper jetting will cause problems as well, such as hard starting, poor throttle response, plug fouling, overheating, lack of power, and more. Too rich and it won’t run right at all. Too lean and it will burn the piston down.

Maybe you’ve never tried tuning a carb before and are afraid that you might mess it up and make it worse. Don’t worry, everyone thinks that before they get started!

I want to show you how to start making your 4 stroke jetting better in just a few minutes with a free guide that you can grab here!

How to prevent coolant from leaking out of the overflow

If coolant is weeping out of the overflow tube on a hot day, a simple fix to keep the temp down could be a high-performance motorcycle or dirt bike radiator coolant, such as Engine Ice (Amazon). It can reduce your engine temps by 10-20 degrees, and the boiling point is higher than most other coolants.

Overheated Engine 2 8 DEADLY Signs Your Dirt Bike Is Overheating [& Why]
2-stroke piston from overheated engine (happens to 4-strokes too)

Adding a fan kit for low-speed riding

Maybe you’re trying to ride faster to keep the radiators cool, but you’re riding narrow trails that force you to slow down if you don’t want to ride over your skill level and crash! Don’t worry, a Tusk Universal Radiator Fan Kit (Amazon) is a fairly simple way to greatly reduce your dirt bike’s operating temp.

It’s made to fit on virtually any liquid-cooled dirt bike, and the fan is made it turn on at a certain temperature, so you don’t have to worry about forgetting to turn it on and overheating.

Catching & recycling lost coolant

Maybe your dirt bike doesn’t have any actual problems, but it still loses coolant every ride and you don’t want to keep adding expensive dirt bike coolant. What if you could catch all of the coolant that goes out the overflow so that it goes back into the radiator?

If your dirt bike doesn’t have one already, you can install a Motion Pro coolant recovery tank (Amazon) onto virtually any 2 stroke or 4 stroke dirt bike. It’s an inexpensive way to keep all of your coolant so you don’t have to top it off after (or during!) your trail ride.

Still getting hot on tight & technical trails?

Maybe you already have a radiator fan and the best coolant, but your dirt bike is still overheating on tight or technical hard-enduro-type trails. This forces you to constantly stop and let your bike cool down if you don’t want to seize it, which is frustrating for you and your buddies because they have to wait for you all the time!

Signs Of Dirt Bike Overheating 8 DEADLY Signs Your Dirt Bike Is Overheating [& Why]

Don’t worry, it’s a common problem, especially on a modern 4-stroke, but what you may not realize is that the main problem is the engine oil is heating up the entire engine.

You see, when you use and slip the clutch to keep your bike going and prevent stalling, this quickly heats up the engine. So, a FREE way to prevent overheating is simply improving your clutch control.

Race Gas Runs Cooler

Another way to cool a bike down is with different gas. I wouldn’t necessarily recommend this for that sole purpose, because if your bike regularly overheats then it has bigger problems.

Higher octane gas, such as race gas (Amazon), will make your bike run a little cooler. Although, doing this will require re-jetting.

Higher octane gas burns at a slower rate, reducing the engine temperature. But, if you keep the previous jetting, it will be on the rich side because it’s putting more gas into the engine than it can burn.

Race gas is used by many racers to help make their bike run better (instead of nasty pump-gas), and probably cooler.

How to prevent overheating and crashes??

As you just learned, your dirt bike needs enough air to keep it running cool, but there’s another free way to prevent overheating. It starts with your riding technique.

Want to learn the basic riding techniques that give you more control, help prevent overheating, and make dirt biking safer in just a few minutes? Click here to learn more.

Darren jones

Monday 20th of February 2023

Hi ive just bought a 2014 ktm 450 sxf and it rides fine but when i start the bike if i leave it for longer then 5 minutes idling it gets very hot and coolent bubbles and comes out of the over flow pipe wot could this be any help would be very much appreciated thanks. daz

Kelley Fager

Tuesday 21st of February 2023

Hey Darren, that's common on a modern 4-stroke MX bike - just don't let it idle that long. It needs airflow to cool it down. Thanks for reading my article!


Tuesday 3rd of May 2022

Hey, I've rebuilt rmz 250 2011 and since I noticed it's definitely running lean, sitting in stagnant air it overheats and the rad smokes a lot and a bit out the breather hose, none out the exhaust, definitely smells sweet out the breather. Exhaust smoke looks completely normal to me. I'm thinking it could be the water pump? When I rebuilt the engine I didn't mess with the water pump so it's definitely due a service. Whenever I leave my bike for a few hours and re check the level it's gone down maybe half an inch or an inch. What does this sound like to you?

Kelley Fager

Friday 6th of May 2022

Hey Adam, that's typical of a 250F mx bike. Have you tried adjusting the fuel screw to richen it up? If it only overheats when sitting then my guess is it's not the water pump.


Wednesday 23rd of March 2022

hey I have a 2007 Suzuki rmz 250 and it gets so hot the coolant pours out and it's smoking and when I turn the bike off it's harder to kick even with the hot start. I wouldn't think that the head gasket is worn out since it's probably only got around 20 hours on it. Does anyone have a clue to what my problem might be?

Kelley Fager

Wednesday 23rd of March 2022

Hey Ian, sorry to hear about your bike problem. Did your bike just start doing this? Did you do anything to the bike before it started happening?


Wednesday 4th of November 2020

It's very hard to believe that simply using performance coolant can reduce running temperatures up to 50 degrees. That is a radical difference.

Kelley Fager

Wednesday 4th of November 2020

Hey Gus, I know it's hard to believe, but that is what Engine Ice claims about their coolant. It's obviously comparing temps in extreme conditions, so the average difference from another coolant may be a lot less than 50 degrees.


Monday 11th of January 2016


Og mechanics

Thursday 26th of March 2020

Read the article it's your head or base gasket dummy