The engine has a closed crankcase ventilation system, which operates due to vacuum in the intake pipe and air filter
Scheme of the crankcase ventilation system is shown in the figure
When the engine is running at low loads and in idle mode, gases from the crankcase are sucked out through a calibrated hole with a diameter of 2 mm in the carburetor throttle body through pipeline 2 into the intake pipe.
In other engine operating modes, most of the gases are removed through pipeline 1.
To separate oil droplets (which are suspended in crankcase gases) and to reduce the ingress of dust and dirt into the engine crankcase when the vacuum in the intake system increases, for example, when the air filter is clogged, a crankcase vacuum regulator is installed, located in the front cover of the box pushers.
When the vacuum in the intake system increases, the membrane with the shut-off valve 7 under the action of the vacuum, overcoming the force of the spring 8, moves towards the valve seat 7, blocking the inlet to the spring seat, thereby reducing the flow of crankcase gases and maintaining an optimal vacuum in the crankcase.
When the inlet is completely closed, gases from the crankcase enter the spring seat only through the calibrated hole 9.
Maintenance of the ventilation system consists in cleaning the pipelines (hoses) and calibrated hole 9 and flushing the parts of the vacuum regulator.
For flushing and cleaning, the vacuum regulator must be removed from the engine and disassembled.
When assembling the vacuum regulator, it is necessary to ensure the tightness of the connection between the housing and the cover.
During operation, do not violate the tightness of the crankcase ventilation system and do not allow the engine to operate with an open oil filler neck - this causes an increased emission of toxic substances into the atmosphere.
On a running engine with a good ventilation system, there should be a vacuum in the crankcase within 10-40 mm of water column, which can be determined using a water piezometer connected to the oil level indicator socket on the cylinder block.
If the system is faulty, there will be excess pressure in the crankcase.
This is possible in case of coking of the ventilation channels, due to significant wear of the cylinder-piston group, in which there is an excessive breakthrough of gases into the engine crankcase.
Increased vacuum in the crankcase (more than 50 mm of water column) indicates a malfunction of the vacuum regulator.
In this case, it is necessary to flush the parts of the vacuum regulator and clean the hole 9.