In air-cooled engines, the cylinder is installed on the crankcase side with a gasket, unlike the cylinder head side, which is supposed to be installed without a gasket. Between the cylinder and the crankcase is a thin paper gasket, which provides the seal. The gasket is as thin as possible so as not to affect the compression ratio. It is therefore not necessary to take it into account when calculating the desired compression ratio.
On water-cooled boxer engines (WBX), this is not a paper gasket but a rubber sealing ring which is fitted without a liquid seal.
Note: On air-cooled engines, no liquid seal is used at the factory. With age, the interfaces become increasingly corroded, which cannot always be absorbed by the seal. It is therefore advisable to rub the paper gasket between your fingers with liquid gasket (listed in the "options" tab).
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