Remove piston rings.
Remove the pin circlips from the lugs on the bosses using a scriber.
Clamp the connecting rod in a vertical position in a soft-padded vise and, using an appropriately sized mandrel, press out the piston pin.
Checking the technical condition of parts
Mounting clearances, allowable wear and grinding limits are indicated in subsection «Detailed Specifications».
All operations for checking and repairing the cylinder head are described in beginning of this section.
Assembling the connecting rod and piston group
Make sure the connecting rods are in the same weight group: connecting rods without bearing shells should not differ in weight by more than±4 g. Check the weight group color marks on the connecting rods. If there are no marks, compare the connecting rods by weight, using one of them as a reference.
Check up a condition of plugs of the top heads of rods. When replacing the connecting rod head bushing, the lubrication holes in the bushing and connecting rod head must be aligned. To do this, it is necessary to shift the lock of the sleeve by 90°relative to the hole in the upper head of the connecting rod (see photo).
The connecting rod bushings are factory bored exactly to the outside diameter of the piston pins. Nevertheless, the fit of the pin to the bushing should be checked. For proper mating, it is necessary that the piston pin, lightly lubricated with animal fat or engine oil, enter the sleeve bore by simply pressing the thumb. If necessary, bore a hole in the connecting rod bushing.
Check the concentricity of the centers of the holes of the connecting rod heads and the buckling of the connecting rod (see figure and values in subsection «Detailed Specifications»).
Make sure the pistons belong to the same mass group, which is marked with marks «+» or «—» on the bottom of the piston.
Check clearance between piston and cylinder (see value in subsection «Detailed Specifications») by measuring the outside diameter of the piston at a distance «A» from the piston skirt (see photo).
On models «518» And «520» also check the distance between the top of the piston pin hole and the piston crown (see photo).
Install the retaining ring in the annular groove of the piston boss from the side opposite the arrow for orienting the piston in the cylinder, stamped on the piston crown.
Clamp the connecting rod vertically in a soft-jawed vise with the oil hole in the upper end of the connecting rod towards you.
Lubricate the connecting rod bushing and piston bosses with engine oil.
Slide the piston onto the connecting rod with the arrow pointing towards you to orient the piston in the cylinder. Insert the piston pin into the piston bore until it stops against the installed circlip.
Install the second retaining ring in the annular groove of the piston boss.
Similarly, assemble other pistons with connecting rods, install liners in the connecting rods and connecting rod caps. Temporarily tighten the connecting rod bolts.
Since 1978 model year, the value of the dimensions has changed «A» (see values in subsection «Detailed Specifications»).