Checking the tightness of valve seats

Coat the valve seat surfaces with a thin layer of lapping paint.

Clean the valve seat in the cylinder head and insert the valve into the guide sleeve.

With light pressure on the valve head, turn the valve about a quarter of a turn and pull it out.

The visible circular pattern on the surface of the seat in the cylinder head makes it possible to conclude that the valve seat is tight.

If the surface of the seat is covered evenly over the entire surface with lapping paint, then the valve seat is tight. If stains remain without paint, then further lapping is required.

Checking with valves installed

Position the cylinder head so that both intake ports or the exhaust port are at the top.

Pour some gasoline into the channels.

Fuel must not enter the combustion chambers.