Cleaning
1. Remove the remnants of the old gasket from the cylinder head.
2. Clean the carbon from the combustion chambers, then wash the head in an appropriate solvent.
3. Remove carbon deposits from the valve, possibly even with a wire brush.
Examination
Cylinder head
1. Carefully inspect the cylinder head for cracks or other damage. If there are cracks, the head must be replaced.
2. Using a metal ruler and feeler gauge, check the flatness of the mating surface of the cylinder head. If the flatness exceeds the allowable limits, it is necessary to regrind the head, while its height must correspond to the required values.
3. Check the condition of the valve seats. If they are burnt, worn, or defective, they must be replaced. If the wear of the valve seat is negligible, they must be lapped. Check the valve guides for wear by inserting the valve stem into them and moving it to the side. The movement should be small. If movement is excessive, remove valve and measure valve stem diameter. Replace valve if necessary. If the valve stem is not worn, the guide bushing is worn and needs to be replaced. Valve guides should be replaced at a service station.
4. If the valve seats must be reground, this operation must be carried out after the installation of new valve guides.
Valves
1. Check each valve seat for localized corrosion, burns, cracks, and general wear. Check the valve stem for wear and bending. Check valve stem end wear. If there are any defects, the valve must be replaced.
2. Using a micrometer, measure the diameter of the valve stem at several points along the length of the stem. Any significant difference in the data obtained indicates wear on the valve stem and a mandatory replacement of the valve.
3. Measure the width of the edge of the valve disc. If the width of the edge of the valve disc is less than the permissible limit, the valve must be replaced.
4. If the valves are in satisfactory condition, they should be inserted into their places and lapped. If the valve discs or seats are badly worn, they must be machined or even replaced before lapping.
5. Lapping of valves is performed as follows...
5a. install the cylinder head with the combustion chambers up on wooden blocks.
5 B. Lubricate the valve seat and valve seat with lapping paste. Reinstall the valve and place the suction cup with holder on the valve plate. Rotate the valve with the suction cup in different directions, lap the valve, and periodically it is necessary to lift the valve to redistribute the lapping paste.
5th century If coarse lapping paste is used, lap until a uniform matte surface appears on the valve seat and valve. Then wipe off the paste compound used and repeat the lapping process with the fine paste.
5g Lapping until a light gray matte color appears.
5d. Carefully remove traces of lapping paste using an appropriate solvent.
Valve elements
1. Check the valve springs for signs of damage and measure the free length of the spring.
2. Install the springs with one of the ends on the frame, check the deviation of the spring axis from the vertical plane. If one of the springs is damaged, all the springs in the set must be replaced.
3. Replace oil seals regardless of their condition.