Blown Motorcycle Head Gasket: Symptoms and Replacement

On a motorcycle, the engine head gasket plays a critical role in maintaining an airtight seal between the lower part (the engine block) and the upper part (the cylinder head) of the engine. However, because the gasket is subject to high temperatures and pressure, it can break down over time, causing serious engine problems.

In this article, we will look at the common signs of a blown motorcycle head gasket; early recognition of these signs is key to preventing greater and more costly damage. We will then give you detailed instructions and practical tips for replacing a blown head gasket correctly.

Engine head gaskets: What they are, what they do, and problems that can occur

The engine head gasket is a critical part that is found in internal-combustion engines. It is situated between the engine block and the cylinder head itself. It consists of a flat gasket, typically made of high-quality composite materials, and it is designed to maintain an airtight seal between the two key engine components: the block and the head.

The head gasket has two main functions:

• it keeps the oil circuit and the cooling circuit separate so that oil and coolant do not come into contact with each other, and
• it applies an airtight seal to the cylinders’ combustion chambers so that they do not experience pressure leaks.

One of the most common problems that affect engine head gaskets is blowouts. When a head gasket is blown out, it loses its sealing ability, causing pressure leaks and potentially letting different fluids, such as oil and coolant, mix together.

The causes of engine head gasket blowouts

In most cases, head gaskets blow out due to engine overheating. The engine can overheat when it is kept at high RPM for a long time or there is not enough coolant. Therefore, it is important that you don’t overwork your bike’s engine. In particular, when the time of the year for nice riding weather arrives, check that your coolant is up to the right level and top it up if necessary.

The seal of the engine head gasket can also break down due to wear. The head gasket, like other gaskets on a motorcycle, is subject to natural deterioration due to the passage of time and repeated use. In the case of a street bike, proper maintenance and replacement are important to keep the bike running smoothly.

The situation is different with off-road motorcycles. In the case of motocross and enduro bikes, the engine is typically single-cylinder, so it is subject to greater stress than the engine of a street bike would be. Also, the engines of off-road motorcycles get opened up and checked more often, and the engine gaskets get replaced regularly, so problems like blown engine head gaskets are rare in off-road bikes.

Identifying a blown head gasket: The signs

There are a number of signs that a motorcycle’s head gasket is blown. We will list them here.

• Difficulty starting the engine. This is due to a loss of compression inside the combustion chamber of the cylinders, which makes it more difficult to initiate combustion. Also, depending on the severity of the failure in the head gasket, there may also be a loss of coolant or oil, in which case one or more cylinders might stop working because no combustion is taking place inside them.
• White smoke in the exhaust. This happens when the head gasket allows coolant to enter the cylinders, where it burns and produces a characteristic white smoke.
• Increased coolant consumption without any sign of external leaks. This occurs because the gasket has lost its sealing capacity.
• Presence of a slimy, foamy substance — similar in appearance to a milkshake or mayonnaise — on the underside of the oil cap. This material forms when coolant mixes with the engine oil.
• Oil spots under the bike when it is parked.

Can a motorcycle be ridden with a blown head gasket?

If you notice any of the signs listed above, it is best to stop the bike as soon as possible. Using a bike with a blown head gasket is not recommended, since the engine loses its airtight seal, allowing combustion gases and coolant to get into the cylinders. Once the oil is contaminated by coolant, it loses some of its lubrication capacity, so that the more the bike is used, the higher the risk of serious damage to the engine.

To sum up, if you think or know that your head gasket is blown, it is essential that you stop immediately and have the engine checked and repaired by an experienced mechanic.

Replacing the head gasket on your motorcycle: How to do it

To quickly check the condition of the head gasket, carefully follow the steps and safety instructions listed below.

• To keep yourself safe while checking the gasket, before you check it make sure that the engine is completely turned off.
• After making sure that the engine is cold, locate the radiator cap and remove it carefully.
• Start the engine and let it idle. Wait for it to warm up a little, and then check to see if there are any bubbles. While you are checking, don’t speed up the engine.
• While the engine is running, look carefully at the coolant inside the radiator. If you see bubbles forming there continuously, this could mean that the head gasket is damaged and blown.

If you find that the gasket is blown or damaged, then it needs to be replaced, since otherwise it could cause compression loss and possibly damage the engine. Replacing the gasket is complicated, and requires technical skills and the right tools. If you decide to do it on your own, then on the Athena website you’ll find a wide range of engine head gaskets — both stand-alone gaskets and kits — that can maintain optimal compression in your engine.

To start replacing the gasket, first make sure that the engine is completely cold so that there is no risk of you being burned or injured. Then you need to remove the cylinder head cover, the fuel system, the exhaust system, and everything else that blocks access to the cylinder head.

Once you have done all this, start on the actual removal and installation process, which consists of the steps listed below.

• Remove the spark plug wires as well as any electrical connections that need to be removed. Then remove the mounting screws and bolts that hold the cylinder head in place.
• Very carefully remove the old gasket from the surface of the cylinder head. Be sure to thoroughly clean the contact surface of both the cylinder head and the engine block.
• Place the new head gasket on the contact surface of the cylinder block in a precise manner, making sure that it is lined up correctly and perfectly centered.
• Put the cylinder head back on the gasket. Screw the mounting bolts back in, doing so evenly and in accordance with the manufacturer’s specifications. Tighten them using the recommended torque and tightening order, since this will prevent damage to the gasket and the engine.
• Reinstall all the external components that you had previously removed, such as the cylinder head cover, fuel system, exhaust system, and electrical connections.

At that point, don’t forget to check and test the engine to make sure that you carried out the gasket replacement procedure correctly. Check that the engine has an airtight seal and that the engine components function properly.

It is important to point out that replacing a head gasket is a technical, complex operation, and that any mistakes made in carrying it out could cause serious damage to the motorcycle’s engine. Therefore, we strongly recommend that you have the gasket replaced by an expert motorcycle mechanic who has the right experience and tools for carrying it out correctly and safely.