Piston pins are installed with an interference fit in the upper heads of the connecting rods and rotate freely in the piston bosses, so heat the upper head of the connecting rod to a temperature of 250˚ C

When assembling, it is convenient to use the Mot. 574-22 and tool Mot. 574-24.

Disassembly and testing of the BPG of the K4M engine was discussed in the article - "Disassembly and troubleshooting of the BPG".

Visually check the condition of the connecting rods (twisting and bending) and the cleanliness of the bearing surfaces of the connecting rod cap and crank head.

Use a 1500W hotplate to heat the top end of the connecting rods.

Place the upper connecting rod heads on the tile.

Make sure the top ends of the connecting rods are in full contact with the tile.

Place a piece of tin solder as a temperature indicator on each connecting rod head.

The melting point of tin solder is approximately 250°C.

Heat the top ends of the connecting rods until the solder melts.

Piston pin preparation

Check if the piston pins rotate freely in the bosses of the respective new pistons.

For installation, use the C13 and A13 drifts from Mot. 574-22 for piston pins without collar or mandrel C13 and A13 from Mot. 574-24 for collared piston pins.

Assembling the connecting rod and piston group of the K4M engine

Install the piston pin (1) on the mounting mandrel (2) (see fig. 1).

- Turn the mandrel (З) until the assembly is tightened.

- Loosen the mandrel (2) a quarter of a turn.

Position of pistons in relation to connecting rods

Pistons are marked with a "V" on the head, which should be on the flywheel side.

Assembling the connecting rod and piston group of the K4M engine

- Position the piston head with the “V” mark up (see 1, fig. 2).

- Direct the groove under the retaining rod of the connecting rod bearing down (see 2, fig. 2).


Assembling the connecting rod and piston group of the K4M engine

Mount the ring B10 (see 1, fig. 3) on the prism, the piston resting on the ring and fasten all the parts with a clamp (2).

Make sure the piston pin hole aligns with the B10 ring hole.

Lubricate the mandrel and piston pin with engine oil.

Leave the piston pin in the assembly and check if it rotates freely. Center the piston if necessary.

The following operations must be done quickly to prevent the connecting rod head from cooling down.

When the piece of solder melts, remove the solder.

Insert the centering mandrel into the piston,

Insert the correctly oriented connecting rod into the piston.

Quickly press the piston pin into the bottom of the tool until the centering mandrel stops.

Make sure that the piston pin does not protrude from the piston in any position of the connecting rod.

Piston ring installation

The piston rings are matched to the piston and must move freely in the piston grooves.

Observe the direction of installation of the rings (the “TOP” mark must be directed upwards).

Assembling the connecting rod and piston group of the K4M engine

Respect the position of the lock of each ring (see fig. 4). The locks of the compression rings must be rotated by 180˚, the locks of the parts of the oil scraper ring by 120˚.