The technical maintenance method for the valve distribution mechanism of a single cylinder diesel engine can be briefly explained as follows, using a single cylinder 165F air-cooled diesel generator as an example:
(1) Precautions for disassembly and assembly
1. In order to ensure the timed opening and closing of diesel engine valves and coordinate with the operation of the crank connecting rod mechanism, it is necessary to align the mark "0" on the crankshaft timing gear and camshaft timing gear.
2. The valve guide should protrude 14.10mm from the outer surface of the cylinder head. Excessive length can easily cause the rocker arm to break or the push rod to bend; If it is too short, it can easily cause carbon buildup in the valve. The valve stem should be able to move freely in the valve guide. If the gap is too small, the valve stem is prone to getting stuck; if the gap is too large, the oil can easily leak into the cylinder.
3. There is a valve guard tube on the outside of the valve stem of the diesel generator. The oil mist from the crankcase flows into the valve chamber through this protective tube to lubricate parts such as the valve and rocker arm. There are O-ring rubber seals on both ends of the valve stem guard tube, which should not be omitted during assembly, otherwise it will cause oil leakage and various parts inside the valve chamber will not be lubricated.
4. When the valve seat is damaged and needs to be replaced, the valve cover should be heated in engine oil to above 100 ℃, and then the cold valve seat ring should be pressed in. After reaming, it should be paired and ground with the valve. After installation, the valve should be 1.8-2.1mm higher than the plane of the cylinder head.
(2) Diesel generator valve clearance adjustment
1. Shake the crankshaft, and when there is significant resistance, that is, the piston is near the top dead center of compression. Then slowly shake the crankshaft and observe from the inspection hole of the air guide cover, aligning the "0" mark on the flywheel rim with the mark on the fixing plate.
2. Loosen the locking nut of the valve adjustment screw, place a 0.1mm thick feeler gauge between the rocker arm and the end of the valve, and then rotate the adjustment screw. When there is a slight stickiness when pulling the feeler gauge, hold the screwdriver and tighten the locking nut.
3. Shake the crankshaft several times until the piston is at the compression top dead center position, then recheck with a feeler gauge.
(3) Inspection of valve grinding and tightness. After about 500 hours of operation of the diesel engine, due to the wear of the valves and valve seats, the valves may not close tightly, resulting in difficulties in starting the diesel engine, increased fuel consumption, and decreased power. Therefore, it is necessary to restore the sealing of the fitting surface through grinding.
Before grinding, remove carbon deposits and clean all parts. Apply a layer of grinding sand on the valve slope and a little engine oil on the valve stem. After inserting the valve into the valve seat, use a leather bowl to suck in the valve, and make about 1/3 turn of forward and reverse rotation while tapping.
First, use a thicker grinding paste, then use a finer grinding paste to grind until a neat gray ring appears on the inclined surface of the valve and valve seat. After washing the grinding paste, apply engine oil and grind for a few minutes. After grinding, the valve can be checked for tightness using the following two methods.
1. Use a soft pencil to draw more than ten straight lines evenly along the longitudinal direction on the inclined surface of the valve head, then gently tap the valve into the valve seat several times (without turning). If all straight lines are interrupted in the ring after removal, it indicates that the valve is well sealed.
2. Assemble all the parts of the valve assembly and add a small amount of gasoline or kerosene from the intake and exhaust pipes. After 3-5 minutes, if there is no oil leakage between the valve and valve seat, it indicates good tightness.
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