The mounting method of the left and right crankshaft bearings of the four-stroke engine is different from that of the crankshaft bearings of the two-stroke engine. There is a sliding fit between the left and right crankshaft bearings of the four-stroke engine and the crankcase bearing seat.

The interference fit between the crankshaft bearing and the crankcase housing of a two-stroke engine (heating the crankcase to mount the bearing) means that the bearing is fixed in the housing.

In the process of maintenance of the two-stroke engine and replacement of the crankshaft, if the operation is not standardized or the crankcase is disassembled many times, the crankcase bearing seat is easy to be stretched, the bearing outer circle is loose (the bearing outer circle rotates with the crankshaft), and the "running outer circle" fault occurs. The crankshaft bearing "runs out of the circle", which affects the accuracy of the crankshaft, the operation of the piston and the power of the engine. In serious cases, the crankshaft produces large noise, excessive wear and partial wear of the cylinder and piston components, resulting in a decrease in the power performance of the motorcycle and an increase in fuel consumption.

To eliminate the crankshaft bearing "running out of the circle" fault, the need to replace the crankcase, part of the engine crankcase can not be found, the method of electroplating bearing outer circle to eliminate the bearing running out of the circle fault, which is characterized by: economic and practical, does not affect the crankshaft operating accuracy, low cost.

Electroplating method to eliminate the bearing "out of the circle" fault

1) Tear down the crankshaft bearing, and test the bearing accuracy after cleaning (bearing wear should be replaced).

2) Machining 2 disks with a thickness of 2mm according to the outer diameter of the bearing, and machining 1 small hole with a diameter of 6mm in the middle of the disk.

3) The processed disc is placed on both sides of the bearing, and M6 screws and nuts are used to fix the disc on the bearing. The purpose is to prevent the ball and seat of the bearing from being electroplated during electroplating.

4) Copper plating on the bearing outer circle (the thickness of the bearing outer circle coating can reach 0.14mm), and the thickness of the coating should be determined according to the wear amount of the crankcase. After the outer circle of the bearing is electroplated, the crankcase is heated to about 100℃, and the bearing is installed in the bearing seat after the oil is applied to the outer circle of the bearing. After the crankcase temperature drops to room temperature, the crankshaft can be installed and the left and right crankcase can be assembled.

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