These aluminum sealing rings are used for two purposes. On all Type 1 and Type 3 engines for sealing the oil pressure pistons at the bottom of the engine, and on Type 3 engines for sealing the auxiliary heater fuel intake line.
Due to the choice of material, notably soft aluminum, they form to the materials between which they are pressed, and ensure the seal. Once disassembled, they are deformed, and if you use them again, the risk of leakage is very high.
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