Expert Advice
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Real tricks and falshoods for perfect exhaust maintenance
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The exhaust is an essential component of the two-stroke engine whose efficiency is tied to multiple parameters such as shape, inner pipes, materials, etc. With use, the exhaust wears, loses its properties and needs to be replaced. However, there are little tricks that maintain its efficiency and optimise the way it works. Eligio Torreggiani, the owner of Elto Racing, one of the leading companies in the production of two-stroke engine exhausts for both karts and motorcycles, tells us about them.
The exhaust regulates the passage of combustible gases from the engine to the outside environment. In addition to carbon particles, these gases also contain unburned oil and mixture, since combustion is never 100% perfect. These residues are deposited on the exhaust cone and, over time, begin to block the holes, thereby modifying and limiting the flow of outgoing gas. When this becomes excessive, the exhaust usually needs to be replaced. Some do resort to burning it, for example by putting it in the fireplace. Aside from not being safe, I also don’t think it’s very wise: while the flames can remove deposits from the holes, they also changes the structure of the metal sheet and, consequently, the properties and performance of the exhaust itself. I would recommend using soda-based products instead.
Spraying the exhaust when warm, although not hot, using WD40 can protect it from oxidation and the formation of rust. However, you should be careful not to overdo it and only use a slight amount of product: indeed, an excessive amount of WD40 would be absorbed by the metal and could change the properties of the metal sheet so that the exhaust no longer makes its distinctive sound, i.e. it no longer produces the proper resonances for optimum engine performance. It is also true that the formation of rust on the exhaust changes its properties and affects performance. I won’t even mention painting it, which would be an absolute disaster!
First of all, you have to check that the welds are intact, but truly understanding if the exhaust has had a hard life on the inside is not easy. If it makes a muted sound when tapped, then that might be an indication, but the best thing you can do is check the points where the exhaust is connected to the curved engine exhaust pipe and, in the case of KZs, the curved pipe that connects it to the silencer: the play between these components is an indication of the amount of wear. If the interior of the exhaust is worn at these points, it means that it has had a very hard life and should probably be replaced. In addition, the exhaust manifold located on the cylinder of the engine has a conical section and if it is worn the seal is no longer guaranteed.
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