The timing mechanism is driven by a toothed belt 6 from the pulley 1 of the crankshaft

The tension of the toothed belt is controlled by the eccentric bearing of the tension roller 5

The toothed belt is closed with special covers - the bottom cover is aluminum, the top and middle are plastic.

The fan drive bearing is located in the bottom cover.

Timing gear

Steel camshaft with hardened cams.

The speed sensor sprocket is mounted on the rear end of the camshaft. A toothed belt drive pulley is installed at the front end.

The valves have a heat-resistant plate welded to the valve stem, the valve stem is chrome-plated. Valve springs are helical with variable pitch.

The valves are driven by lever 2 from the camshaft cam.

The clearance in the valve mechanism is adjusted by adjusting screw 2 with a ball head through a special hole in the lever.

The adjusting bolt is fixed by means of a special profile of the threaded insert inside the sleeve 4.

valve actuator

Dimension A: for inlet valves 0.15 + 0.04 mm; for outlet valves 0.30 + 0.04 mm

Maintenance of the gas distribution mechanism

Maintenance of the gas distribution mechanism consists in periodically checking and, if necessary, adjusting the clearances in the valve drive, as well as checking and, if necessary, tensioning the timing belt of the camshaft drive.

Check and adjust the gaps between the valve levers and the backs of the camshaft cams on a cold engine with the camshaft housing bolts tightened and the timing belt tension of the camshaft drive adjusted.

To check and adjust the clearances in the valve drive, you must:

- provide access to the cover of the camshaft housing and remove the cover;

- set the piston of the first cylinder to the TDC of the end of the compression stroke, for which turn the crankshaft by turning the generator pulley with a key (if necessary, tighten the belt tension by hand, pressing the belt against the pulleys) so that the flat with the number I on the camshaft is directed up, and the mark on the camshaft pulley is aligned with the upper edge of the camshaft housing;

- check the gaps between the backs of the cams and the valve levers of the first cylinder with a feeler gauge. For the intake valve, the clearance should be

0.15-0.19 mm, for graduation - 0.30-0.34 mm. If necessary, adjust the gaps by turning the adjusting screw 2 with a TORX key;

- turning the crankshaft 180 ° clockwise, check the valve clearances of the third, fourth and second cylinders one by one.

The tension of the toothed belt of the camshaft drive must be within 50 ± 5 daN (50 ± 5 kgf), which corresponds to the green zone of the instrument scale.

Due to the complexity of performing these works and the need to use a special tool, it is recommended that the gas distribution mechanism be serviced at a specialized service station (SRT).

Checking Timing Timing Belt Tension