OHV engine
As part of maintenance, valve clearances must be checked every 15,000 km and adjusted if necessary. The valve clearance must always be checked on a warm engine after repairing the cylinder head.
The adjustment of the valves only has the desired result if the valves seal perfectly, do not have unacceptable play in the guides and the ends of the rods are not broken.
If the gap is too small, the valve timing changes, compression worsens, engine power decreases, the engine runs unstably. In extreme cases, the valves may be deformed or the valves or valve seats may be burned.
With a large gap, strong mechanical knocks occur, the valve timing changes, due to a lean working mixture, the engine develops less power, the engine robot is unstable.
Remove the air filter see paragraph 4.44.
Remove cylinder head cover.
Check valve clearance at operating temperature (approximately 80°C - coolant and 60°C - oil) and a running engine with the appropriate probe:
- Exhaust valves 0.25 mm.
- Inlet valves 0.15 mm.
The feeler gauge should move with difficulty between the rocker arm and the end of the valve stem.
In the direction from the front of the engine, the valves are arranged in the following order: 1st cylinder is exhaust, intake, 2nd cylinder is intake, exhaust, 3rd cylinder is exhaust, intake, 4th cylinder is intake, exhaust.
If the gap is incorrect, it can be adjusted by turning the rocker nut.
Attention: Oil splashes from the rocker arm can be removed with a piece of cardboard (approx. 40x320 mm), which is installed between the sealing surface of the cylinder head cover and the push rods.
Screw on the timing cover with a new gasket.
Install the air filter with heating hose, see paragraph 4.44.
ONS engine
Thanks to the installation of hydraulic compensators, there is no need to adjust the valve clearance.
Attention: Hydraulic valve clearance compensators with high oil levels can cause noise in the valve train. In this case, the engine oil level should first be checked and corrected if necessary.
Valve stem play:
- Inlet valves: 0.015 to 0.047 mm
- Exhaust valves: 0.030 to 0.062 mm
Allowable valve stem runout:
- Intake valves: 0.04mm
- Exhaust valves: 0.05mm
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