Sequence of execution
1. Remove the cylinder head ("Cylinder head - removal and installation").
2. We clean the cylinder head from dirt and carbon deposits, wash it from oil deposits, and remove carbon deposits from the walls of the combustion chambers with a metal brush.
3. Carefully inspect the cylinder head. There should be no cracks on them. There should be no burrs or traces of metal drag on the working surfaces of the camshaft supports and the walls of the tappet mounting holes. The valve guides and seats must fit tightly in the head body, without any signs of displacement during the operation of the timing system. The valves and their seats must not have cracks or signs of burning.
4. Check the flatness of the head.
Advice: This requires a special template, but if you don't have one, you can check the lower mating plane of the head with sufficient accuracy using a wide metalworking ruler.
We apply the template (ruler) with its edge to the mating surface diagonally across the head.
We make sure that there is no gap between the edge of the template (ruler) and the plane of the head. The gap can be observed both in the middle part of the plane and at its edges. We measure the gap along both diagonals using a set of flat feeler gauges.
The maximum allowable gap is 0.1 mm.
Recommendation. If the gap is greater than the permissible limit, the head must be replaced.
5. Check the tightness of the cylinder head. To do this, we close the window for supplying coolant to the thermostat using the plug on the end surface of the head.
We turn the head over and fill its internal cavities for coolant with kerosene.
7. Make sure there is no kerosene leak from the cylinder head.
If the kerosene level in any chamber drops, one or both valves are leaky.
Recommendation. If a leak is detected, the cylinder head must be repaired or replaced.
Lapping
1. Remove the oil seal from the valve ("Valve stem seals - replacement").
2. Remove the valve from the guide sleeve.
3. Apply lapping paste to the working edge of the valve.
4. Install the valve into the cylinder head and attach the valve grinding tool to its stem.
5. Pressing the valve against the seat, turn it from side to side. After 10-15 movements, turn the valve 90° and continue grinding.
6. We grind until a uniform ring-shaped mark is formed on the valve plate...
...and his saddle.
7. Remove any remaining lapping paste from the valve and its seat.
8. We grind the remaining valves in the same way.
9. After grinding, re-check the tightness of the valves (see above).
10. If the kerosene does not drain, install new oil seals and valve in the reverse order of removal.