Yaroslavl Engine Plant YMZ-536 Operation Manual
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Contents
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135VALVE TRAIN CLEARANCEADJUSTMENTExpansion gaps in the valve train are essential to ensure leak-proof valve contact with the seat during thermal expansion of thevalve train parts when the engine is in operation.If the clearances are too large, the valve lift is decreased whichresults in worse cylinder filling and cleaning, higher shock loads(valves start knocking) and increased wear of the valve train parts.If the clearances are too small, the valves do not come in tightcontact with the seats during thermal expansion of the valve train partswhich impairs gas dynamic processes in the engine cylinders andengine performance. Moreover, decreased clearances of the exhaustvalves can lead to the valves overheating and burning.Valve train clearances must be adjusted on a cold engine or notearlier than one hour after the engine was stopped. Valve clearanceadjustment must be performed according to the firing order 1-5-3-6-2-4. The cylinder numeration begins from the fan.The clearance between the rocker arm cup and the valve yokemust be: for intake valves: 0.30 – 0.40 mm for exhaust valves: 0.40 – 0.50 mmThe valves located closer to the fan are intake valves; thevalves located closer to the flywheel are exhaust valves.Valve clearance check and adjustment procedure is as follows:1. Prepare the driver’s tool kit.2. Disconnect the gas discharge hose pipe from the cylinder headcover.3. Remove the cylinder head cover fixing bolts; then remove thecylinder head cover.4. Install the crankshaft turning gear (from the driver’s tool kit) intothe hole (fig. 45) as far as it will go, to engage it with the flywheelgear. Remove plug 3 located on the flywheel housing end 1 (Fig.45) on the left engine side under the air break compressor. |
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