Check of pistons and rods

Carry out a thorough inspection of all parts. In the presence of burrs, scratches and wear marks replace them. Measure the vertical gap in the piston ring grooves with probe that is inserted between the plane and the plane of the piston ring groove of the piston ring, as shown in Fig. 58 (grooves must be carefully cleaned before it, this can be, for example, used a broken piston ring). If the measurement results show that the gaps in the upper ring exceeds 0.20 mm, on the average - 0.15 mm and a valve stem - 0.10 mm, this indicates the wear of the piston rings or pistons. Then, the inner side of the crankcase must in turn insert the piston rings in the cylinder bores, and an inverted top piston push them down so that they are horizontally arranged and are spaced 20 mm from the bottom edge of the cylinder liner. Then measure probe gap piston ring, as shown in Fig. 59. In all rings, this clearance is 0.20-0.40 mm. Limits wear to lock the upper rings must not exceed 1.5 mm, for the rest of the rings - 1.0 mm.

Check the piston pin and connecting rod bushing for wear or burrs. In this case, allowed a single replacement of a defective rod, but the weight of the new connecting rod must not be different from the mass of the connecting rod to be replaced by more than 5, the replacement of bushings in the little end recommend at specialized service stations.

Before reuse bolts connecting rod bearing caps, measure the diameter of thin parts with calipers (Fig. 60). If the diameters of measured bolts will be less than 7.1 mm, these bolts must be replaced, which should be carried out according to the instructions below. Before replacing the bolts should perform another test, which is as follows: connecting rod bearing cap is seated on a bolt and turned to the side so that the connecting rod and turn toward the bearing cap is on the horizontal axis, as shown in Fig. 61. If the bearing cover under its own weight falls down, the rod must be replaced by a new one. Otherwise it is necessary to replace the bolts. The device for checking the connecting rods, check all connecting rods to twist and bend, the value of which shall not exceed the minimum acceptable. To perform this work are also encouraged to apply to specialized service stations. When checking the pistons and connecting rods, the following recommendations.

It is not recommended to reuse the connecting rods that were once overheated due to a faulty bearing (connecting rods with discoloration).

The connecting rods and connecting rod bearing caps are matched and labeled.

The new connecting rods are delivered with bore bushings in the upper head and can be installed directly on the engine.

Fit the connecting rod bearing cap bolts with inserts and using Nutromer fathom the inner diameter of the bearing. If the result exceeds the value of 51.619 mm or be revealed some taper, the supporting surface connecting rod bearing cap can be adjusted on a flat plate to 0.02 mm.

If the connecting rod is in perfect condition, and in the piston pin found an increased gap, replace the plug in the top head of a rod, extruded and pressed into the old new. It is necessary to pay special attention to the location of the oil holes in the sleeve. It should be aligned with the arrow marked on Fig. 62. After pressing the new bushings into the top head of a rod it is necessary to expand to a diameter D2, indicated on Fig. 62. In this figure, the permissible diameter.