Piston
Cast from aluminum alloy. To improve run-in, the outer surface of the piston (pic. 5) coated with tin. To compensate for uneven thermal expansion, the piston skirt has a complex shape. The piston has a conical shape: the diameter is smaller at the top than at the bottom. Therefore, it is necessary to measure the piston diameter only in a plane perpendicular to the piston pin and at a distance of 52.4 mm from the piston crown.
The hole for the piston pin is offset from the axis of symmetry by 2 mm to the right side of the engine. Therefore, for the correct installation of the piston in the cylinder, there is a mark shown in the figure near the hole for the piston pin "P", which should face the front of the engine.
According to the outer diameter, the pistons are divided into five classes through 0.01 mm, and according to the diameter of the hole for the piston pin - into three categories through 0.004 mm. Piston class (letter) and piston pin bore category (number) indicated on the piston crown.
Pistons of classes A, C, E are supplied as spare parts. These classes are sufficient for selecting a piston for any cylinder, since pistons and cylinders are divided into classes with some overlap in size. For example, class B and D cylinders can fit a class C piston. In addition, when rebuilding engines, pistons are usually replaced on worn cylinders, so a class C piston can fit a slightly worn cylinder that had a class B. The main thing when choosing a piston is to ensure the necessary mounting gap between piston and cylinder.
Since 1986, repair size pistons for all engine models have been manufactured with an outer diameter increased by 0.4 and 0.8 mm. Until 1986, pistons of the following repair sizes were produced: for engines 2101 - with an increase of 0.2; 0.4 and 0.6 mm; for 21011 - with an increase of 0.4 and 0.7 mm.
Pistons of engines 2101 and 21011 are easy to distinguish from each other in appearance. In addition to having different diameters, the 2101 pistons have a smooth bottom, while the 21011 pistons have a cylindrical recess in the bottom with a diameter of 55 mm and a depth of 1.9 mm.
Piston rings
The piston has two compression rings and one oil scraper. All of them are made of cast iron.
The outer surface of the top compression ring is chrome-plated and barrel-shaped. Lower Compression Ring - Scraper Type (has a recess on the outer surface) , phosphated.
Piston pin
On engines 2101 and 21011, the same steel tubular piston pins 5 are installed. They are pressed into the upper head of the connecting rod 3 and rotate freely in the piston bosses.
According to the outer diameter, the fingers are divided into three categories through 0.004 mm. The category of the finger is marked on its end with the corresponding color: 1st - blue, 2nd - green and 3rd - red.
Connecting rod
The lower head of the forged steel connecting rod 3 is detachable, connecting rod bearings 2 are installed in it. The connecting rod is processed together with the cover 1, so it is not interchangeable with the covers of other connecting rods. In order not to confuse the connecting rod caps during assembly, on the connecting rod and its cap (side) there is a stamp of the number of the cylinder in which they are installed. When assembling, the numbers on the connecting rod and cap must be on the same side.