On some occasions we can find that the motorcycle engine reaches high temperatures, which are not recommended for the proper functioning of the engine. It is not a problem if these appear punctually, but it is a problem if the engine temperature remains high by default.



Why does a motorcycle's engine get hot?

First of all, we will take into account the different systems that the engine uses for cooling:

The first system is the lubricating oil itself, which behaves like an efficient thermal sponge inside the engine. Check that the oil level is within the levels recommended by the manufacturer, an important factor if the motorcycle is only cooled by air, and that its viscosity is recommended. A low amount of oil or a high viscosity can cause a high increase in the operating temperature of the engine.

The second system is the coolant if the motorcycle has a liquid cooling system. This system is designed for high-performance engines, and its correct condition is essential to avoid overheating that can cause the destruction of the cylinder head gasket and/or seizure of the engine due to the loss of tolerances.


How to prevent my motorcycle from overheating?

The first sign of a cooling system failure is the illumination of an overheat warning light on the motorcycle's marker. We must check the proper functioning of the warning light and the temperature sensor, ruling out electrical faults that cause their malfunction.

Check that the condition and level of the coolant inside the radiator and in the expansion tank is correct, and it must be replaced if it has been in operation for more than two years. If the coolant level is low, proceed by filling the coolant up to the level indicated by the manufacturer, checking that there are no air pockets in the hoses that could falsify the check. Once the circuit is filled, we will run the engine for a controlled period of time and recheck the coolant level. If the level is low again, it may be due to a leak in the cooling system.


Refrigeration system leaks can be caused by several factors:


Old or cracked pipes.

Clamps in poor condition.

Damaged joints.

Perforated radiator.

Many of these leaks will only be observed when the engine reaches its operating temperature since the increase in pressure in the system increases the losses of coolant. Other leaks may be due to deteriorated pump seals, a cracked cylinder cooling circuit, or a bad head gasket.

Leaks can also appear due to excess pressure in the system. This high pressure can be due to a faulty thermostat, which is permanently closed, or by leaks from the head gasket, which transfers the pressure of the explosion to the cooling system. The increase in pressure and temperature in the system will cause the violent expulsion of the coolant through the expansion vessel.

The check of the thermostat will be applying heat and watching her reaction. The failure in the cylinder head gasket can be observed if we analyze the coolant since the gases generated by the combustion will contaminate the coolant and cause residues in it.

We must not forget one of the main elements of the system, the radiator. The good condition of this element is essential for the proper functioning of the system, losing its capacity when more than a third of the fins are in poor condition.



A fault in the electric fan or in the thermal contact that triggers it will cause the engine to overheat when driving slowly in the city or for long periods with the engine at idle speed. To test the electric fan, we will bridge its connections to supply direct current from the battery. If the electric fan works in this way, the fault will be in the thermal contact or in the relay that triggers it.

If the electric fan does not react, it may be due to a fault in it or in its winding and must be checked and repaired, or replaced. If the fault is in the thermocontact, we will check its operation by applying heat and observing, through its connection to a multimeter, that it provides continuity with the increase in temperature, thus causing the closing of the circuit and the activation of the electric fan. In the case of not observing reaction of the thermocontact when applying heat, it will be replaced.

In the event that the electric fan is controlled by the electronic control unit, it is activated by means of the signal sent by a thermo-resistance to the control unit to indicate the operating temperature of the engine. The thermo-resistance will be checked with the multimeter to verify that it maintains its values ​​within those indicated by the manufacturer.