The crankcase bleed system consists of an oil separator in the valve cover connected to the air filter with a rubber hose. The reduced pressure in the air filter causes gases to be sucked in from above the valves. This space is connected to the crankcase. During the combustion of the mixture, part of the gases (along with the remains of unburned gasoline) gets between the walls of the cylinder and the piston, under the piston or in the crankcase. It must be possible for these gases to pass freely from the crankcase to the air filter, as increasing pressure would cause oil to escape through the crankshaft seals or other gaskets. Since oil mist forms in the main crankcase during engine operation, the result of clogged air ducts is oil leakage through the weakest gaskets. To prevent this, an air exhaust system is used. In earlier models, the air outlet was screwed to the crankcase. In these models, the air vent is built into the valve cover, where the oil is separated from the passing gas (photo 1.51), which then goes to the main crankcase. Hot oil vapors, as well as exhaust gases, together with unburned gasoline, are sucked into the air filter. This has two advantages: the car emits less pollutants and recycles unburned fuel. By the amount of gases entering the air filter from the main crankcase, it is possible to assess the tightness of the piston-cylinder pair working together. The condition of the wire connecting the valve cover to the filter should be checked periodically. Wire cleaning is only necessary with used motors.
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