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How is a motorcycle engine cooled?

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Refrigeración de un motor de moto

I tell you how the cooling system of a motorcycle engine works, what types exist and what maintenance they need.


Today I bring you a topic from our motorcycle mechanics book. We all have a nightmare: that our bike gets the flu. Precisely the cooling system ensures that this does not happen.

Why is it necessary to cool a motorcycle engine?

The engine houses a veritable inferno inside.

On the one hand, in the combustion chamber (whose name is already frightening), there are thousands of explosions caused by the spark of the spark plug on the mixture of air and gasoline.

On the other hand, the piston goes up and down endlessly inside the cylinder, making metal rub against metal in an endless sequence.

In addition to this, many other parts move and collide with each other without stopping, such as the rocker arms on the valves, the transmission gears or the connecting rods with the crankshaft.

It is logical to think that, in this succession of explosions, rubbing and knocking, very high temperatures are reached.

This is why it is absolutely necessary to cool the engine, to prevent overheating from ruining it forever.

The motorcycle engine cooling system takes care of this.

In what ways can a motorcycle engine be cooled?

There are basically three types of engine cooling:

1) Air cooling

This is the most classic way of cooling an engine. Almost all our classic motorcycles use this system, as it is the simplest.

It is very common to find cylinders with many steel sheets on the outside. These are fins that allow air to circulate between them, cooling the engine as it passes through. It should be remembered that an engine is designed to work in motion, therefore, a motorcycle started for a long time without moving tends to heat up.

The fins are usually painted black to promote heat radiation away from the engine.

It is usually the system used in small engines, and in almost all two-stroke engines.

2) Water or liquid cooling

In this case, a liquid is introduced between the outside air and the engine to help dissipate engine heat.

This liquid is usually distilled water with an antifreeze additive (usually glycol). The additive gives the water the properties of not freezing, not boiling and not oxidizing the cooling ducts.

The basis of the system is the entry of liquid at low temperature into the engine, inside which it performs a path in which it heats up as it cools the engine (the engine temperature is transferred to the coolant).

At the end of its path, it is released to the outside and goes to a radiator. In this radiator, thanks to the ambient air, the liquid cools down again and starts its cycle again.

These systems usually have a thermostat, which keeps the liquid circulating inside the engine until the temperature rises and it is necessary to cool it in the radiator.

motorcycle engine cooling

Checking the coolant level

Unlike air cooling, a liquid cooling system requires maintenance: you should check the coolant level regularly, bleed and change it when necessary and check the thermostat.

You should always check the coolant level when the engine is cold.

When performing this operation, check the condition of the radiator, in case the fins are bent, in which case, you should separate them with the help of a flat plastic tool, being very careful not to damage it.

3) Oil cooling

In addition to the systems listed above, the lubrication oil is the main responsible for the cooling of the engine of a motorcycle, hence its good condition and its periodic replacement is vital.

The oil runs through all the internal parts of the engine, fulfilling its lubrication and cooling function, and finally falls to the bottom of the crankcase.

We've written a motorcycle mechanics book!
I tell you, in words everyone can understand, how each part of your bike works and how to repair it.

Basic Motorcycle mechanics book

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