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Measurement of crankshaft clearance

2020-11-23

The axial clearance of the crankshaft is also called the end clearance of the crankshaft. In engine operation, if the gap is too small, the parts will be stuck due to thermal expansion; if the gap is too large, the crankshaft will cause axial movement, accelerate the wear of the cylinder, and affect the normal operation of the valve phase and the clutch. When the engine is overhauled, the size of this gap should be checked and adjusted until it is suitable.

The measurement of crankshaft clearance includes axial clearance measurement and main bearing radial clearance measurement.

(1) Measurement of axial clearance of crankshaft. The thickness of the thrust bearing plate on the rear end of the crankshaft determines the axial clearance of the crankshaft. When measuring, place a dial indicator on the front end of the engine crankshaft, knock the crankshaft to move it backward to the limit position, then align the dial indicator to zero; then move the crankshaft forward to the limit position, then the dial indicator The indicator of is the axial clearance of the crankshaft. It can also be measured with a feeler gauge; use two screwdrivers to respectively insert between a certain main bearing cover and the corresponding crankshaft arm, and after prying the crankshaft forward or backward to the limit position, insert the feeler gauge into the seventh bearing Measured between the thrust surface and the surface of the crankshaft, this gap is the axial gap of the crankshaft. According to the original factory regulations, the standard for the axial clearance of the crankshaft of this car is 0.105-0.308mm, and the wear limit is 0.38mm.

(2) Radial clearance measurement of main bearing. The clearance between the main journal of the crankshaft and the main bearing is the radial clearance. When measuring, insert the plastic wire gauge (plastic gap gauge) between the main journal and the main bearing, and be careful not to rotate the crankshaft to prevent the gap from changing during rotation and biting the gap gauge. Attention should be paid to the influence of the quality of the crankshaft on the clearance.