8 Reasons Your Dirt Bike Is Overheating & How To Fix Them

Some of the most common causes a dirt bike would overheat are not always so obvious. Here’s what to look for and how to fix it.

If you’re trying to tell if your dirt bike is overheating the signs might only become obvious once your bike starts to boil. By then it might be too late to take preventative action. 4 Stroke dirt bike engines are designed to operate in the temperature range of 82°C – 104°C (180°F – 220°F). Riding your 4 stroke for extended periods at temperatures above this range will cause the engine  in your 4 stroke dirt bike to overheat. On a 2 stroke dirt bike, average riding temperatures can range from 62°C – 82°C (145°F – 180°F) but can increase beyond the point of boiling.

How To Tell If Your Dirt Bike Is Overheating

The most obvious signs that your dirt bike is overheating include the following;

  • Bike is steaming from radiators
  • You can smell the coolant burning (usually a sweetish smell)
  • Coolant may be coming out of the overflow
  • Your engine has locked up and won’t turn over (worst case)
  • Oil is leaking from the seals
  • Loss of power when accelerating
  • Cylinder is hotter than normal

Common Reasons A Dirt Bike Would Overheat

Dirt BIke Radiator cap

There are a number of reasons why a dirt bike might overheat. This could be due to the riding terrain or a fault in the bike. Rough technical terrain can often lead to overheating when the bike’s engine is constantly being pushed into higher revs, which makes the engine have to work harder, without getting much airflow. One of the most common causes of an overheating dirt bike is low or no water-coolant mix in the radiator. Some other common reasons include;

  • Coolant/Water mix is low or empty. Prior to each ride, remove the radiator cap and check that there is enough liquid inside. This can prevent major engine damage. If the radiator is empty after each ride and you constantly need to refill it with coolant, it’s likely that you have a crack. The most common places to find a leak in the radiator will be a blown gasket – either the base, head or water pump – a hole in the radiator, or a hole in the hose.
  • Not enough coolant in the mix. Dirt bikes have a coolant capacity of around 3-4 litres. You can buy premixed coolants or pure antifreeze which should be diluted with distilled water at a 50:50 ratio.
  • Faulty radiator cap. A faulty cap could cause leaks resulting in overheating. A faulty cap can also allow air and liquid to overflow when the pressure build up is too much.
  • Failing water pump. One of the most common reasons for a failing water pump is the seal. This is a quick fix and not too costly. Although if the leak is in a bad position it could mix with the tranny oil leading to corrosion and possible seizure in the long run. A faulty water pump is something that is easily fixed and should be fixed as soon as you notice it.
  • Coolant seeping out of the overflow. There are a number of reasons why your dirt bike could be losing liquid from the overflow. Common causes include a blown head gasket, faulty radiator cap, or your engine is running too hot causing the liquid to boil out. A simple way of detecting this early is to replace your radiator cap with a cap that has a built in temperature gauge. You might also want to consider riding with a radiator coolant specifically designed for higher performance. This can help to drastically reduce engine temperature while riding.
  • Head gasket might be blown. If your bike is still running with a blown gasket, it’s most likely to be leaving a trail of white smoke from the exhaust as it burns off the coolant. A blown head gasket can cause serious engine damage. If a blown gasket is identified and fixed early enough, it should not be too expensive of a repair. A damaged base gasket is a much worse problem to have than a blown head gasket. With a damaged base gasket, the coolant could end up leaking into the transmission oil. With a lack of coolant in the radiators, the piston and cylinder will overheat and seize. Check out this guide to the best replacement dirt bike pistons.
  • Your dirt bike jetting is too lean. With lean jetting, the engine burns more air than fuel. Air gets hotter, faster than fuel does which causes the engine to spike in temperature as it does not have enough fuel to burn. Riding your dirt bike with the jetting too lean can eventually burn out the piston and lead to engine failure. It’s worth putting in the extra time to tune your carb to perfection. This will improve overall ride quality, performance, and reliability.
  • Not enough airflow. Riders often overlook the fact that antifreeze and water are not the only substances that cool the engine. Air flowing over the radiators plays a big part in keeping the radiators cool. Idling or riding around at low speeds can lead to overheating for two reasons. Firstly, there may not be enough airflow to help the cooling process. Secondly, at low speeds there is not enough fuel flowing into the engine which means the engine burns hotter as it burns more air.

Why is My 4 Stroke Dirt Bike Overheating

A common reason for 4 stroke dirt bikes to overheat is due to not enough airflow. If you’ve read our guide to warming up your dirt bike you’ll know that letting your bike stand and idle for too long can cause damage. This is because there is not enough air flowing over the radiators and not enough fuel flowing into the engine. 4 stroke dirt bikes need to be ridden fairly hard, in order to keep the engine cool.

Check out our guide to choosing the best 4 stroke for single track and woods riding.

First Checkpoint

Why is My 2 Stroke Dirt Bike Overheating

The most common reasons a 2 stroke dirt bike would overheat are a faulty cooling system, inefficient engine lubrication, or insufficient air intake. These causes all have something in common. They are all causing the engine to work harder than necessary which causes friction and eventually overheating.

The cooling process has evolved over years. Nowadays, dirt bike engines are cooled in two ways. Air cooled and liquid cooled. Check out this neat video for an explanation

Replacement Parts To Prevent Your Dirt Bike From Overheating

dirt bike radiator braces

There are a few common sense tips that you can use before and during every ride to help prevent your dirt bike from overheating;

  • Change your coolant. Use high quality coolant and make sure you change it frequently. Check your motorcycle’s service intervals.
  • Replace your stock radiator cap with a radiator cap that can withstand higher pressure and has a temperature gauge to help 
  • Protect your radiator with a race brace or guard to prevent damage if you crash.
  • Make sure your water pump is not faulty.
  • Use different fuel. Gas that is designed for racers has higher octane and a lower boiling temperature. Note: changing your fuel will require you to change your carburetor  jetting.
  • Make sure you regularly service your bike and do thorough inspections. A faulty cooling system can cause serious and costly damage.

Riding Tips To Prevent Your Dirt BIke From Overheating

As a rider there are a few simple riding techniques you can implement to help prevent overheating.

  • Avoid letting your bike idle for too long – especially 4 stroke dirt bikes.
  • After technical passes, open up the throttle to allow more fuel to flow into the engine cooling it down. This also helps with airflow over the radiator.
  • Avoid riding the clutch where possible.
  • Don’t double clutch unless you need to.
  • Avoid holding the throttle open when there is no traction (wheel spinning).
  • If your bike does overheat, be careful when opening the radiator cap. Boiling water could spray out.
  • If your bike does overheat without any open area to ride, turn off the engine and let it cool. You could spray some water on the radiator to help.
  • When buying a new bike or doing an engine rebuild, make sure you follow our guide on how to break in a dirt bike engine.

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