2. Measure the piston clearance in the cylinder. If it exceeds the permissible value (0.15 mm), it is necessary to bore the cylinder to one of three increased diameters. The cylinder diameter should be measured at three heights perpendicular to each other.
After boring, the piston mounting clearance in the cylinder should be 0.03 mm.
3. If it becomes necessary to ream the housing, which was previously bored to the last repair size, it is necessary to transfer the housing sleeves. This operation should be carried out by a specialized enterprise.
4. It is necessary to check the cone and oval of the cylinder liners using a micrometer gauge (photo 1.150). The cylinder liner wears out most in the upper part, where the operating conditions are the most severe, i.e. the highest temperature, pressure and the worst lubrication. The first sealing ring reaches a distance of 5 mm from the upper edge of the cylinder liner. Below, a distinct threshold (barrier) will be felt. If it is large, this indicates engine wear. We also measure the liner diameter there.
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5. The diameter measured under the threshold should not differ from the diameter measured at the bottom of the sleeve (where it will wear out the least) more than 0.15 mm.
6. If new pistons are fitted to old bores, it is important that the cylinder walls are slightly roughened, this is done with fine-grained sandpaper. This will allow the piston rings to grind in properly.
7. It is necessary to carefully check for cracks and damage in the crankcase and cylinder block. If necessary, remove the plugs of the oil or water channels, clean them and blow them out with compressed air.
New plugs are usually driven in for the sealing fluid. If there is no doubt about the correctness of the plugs, you can check their tightness. To do this, we supply compressed air to the oil or water channels, and cover the plug with a layer of oil on the outside so that air bubbles are visible, if any. During the check, other channel outlets must be closed. In a similar way, we check for cracks in the housing. We plug all the outlets of the oil and water channels, except for one, through which we supply compressed air. Then we place the housing in water and determine the location of the leak. Since there are a lot of channel outlets on the contact surface of the head, especially water, of various shapes that are difficult to seal, we suggest fitting a piece of rubber and 4-5 mm thick tin. The rubber and tin should have an external shape and size copied from the old gasket from under the head. According to the gasket, it is necessary to redraw the holes for the bolts securing the head on the rubber and tin. Then we drill holes in the designated places and screw the tin with the rubber under it to the body. We seal all the upper holes in this way. If cracks are found, you can try to solder the body at a specialized enterprise.
8. Check the diameter of the holes in the main bearings.
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