Maintenance machining process is not good
Some motorcycle maintenance workers use the iron hammer to strike when overhauling the engine. After the two-stroke engine is disassembled several times, the engine crankshaft rolling bearing hole is enlarged, resulting in poor precision of the rolling bearing. The rolling bearing runs through the hole, which is not correct. The ground is selected to be repaired in the periphery of the inner hole of the rolling bearing by the tin sheet and the punching method, so that the rolling bearing is not the same after the crankcase is closed. There are also some new engine crankshaft parts that need to be replaced during maintenance. The quality of the spare parts is weak, and the motor shaft has different shaft degrees of more than 0.05mm. When the upper and lower crankcases are close together, in the condition that the engine block, the piston rod and the piston ring are not installed, the rotation of the engine crankshaft is inconvenient, and the frictional friction resistance is relatively large, resulting in over-temperature of the diesel engine.
Due to the serious damage of the diesel engine crankshaft connecting rod big head rolling bearing, the upper and lower engine crankshaft rolling bearing installation is not timely, after the engine crankshaft total installation, the vertical axis of the crankshaft connecting rod does not have the engine cylinder management center, causing the crankshaft to tilt up and down, the piston rod is The yaw in the engine block makes the piston ring and the engine block eccentric, and the cylinder pressure is lowered, causing the diesel engine to overheat. The camshaft camshaft of the four-stroke engine engine is seriously damaged, the camshaft has a low aspect ratio, and the lift of the camshaft arm is relatively small, which makes the exhaust pipe encounter resistance and the displacement is insufficient, resulting in over-temperature of the diesel engine. .