A typical bike engine contains around three litres of oil, and one of the biggest challenges to engineers over the years has been to keep that oil where it should be.
There are many joints between the various engine castings, and nearly every one needs some means of preventing fluids from escaping. In an ideal world, every joint face would be perfectly flat, smooth and perfectly aligned with its opposite number. Furthermore, when the bolts were tightened no distortion of the joint would take place and they would remain perfectly tightened throughout the life of the bike. Unfortunately, we do not live in an ideal world and this is where gaskets come in.
The aim of a gasket is to provide a little elasticity to absorb the imperfections found at the joint surfaces. Typically, gaskets are made from a mixture of fibres, such as paper or asbestos, held within synthetic rubber such as nitrile. Nowadays asbestos is no longer favoured and more use is made from up-todate materials such as carbon fibre, PTFE and Kevlar.
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