Removing the cylinder head cover (see Replacing the cylinder head cover gasket).
We turn the crankshaft until the mark on its pulley coincides with the mark on the camshaft drive cover.
Remove the camshaft housing and valve levers (see Removal of a camshaft and levers of a drive of valves of an injection engine, Removing the camshaft and valve levers of the carburetor engine). In this position, the crankshaft (pistons of the 1st and 4th cylinders are at TDC) we change the valve stem seals of the 1st and 4th cylinders.
Insert through the spark plug hole between the piston crown and the valve disc (on which we change the cap) a soft metal bar with a diameter of about 8 mm.
Install the valve dryer.
We rest the thrust bearing of the cracker against the valve plate, and we wind the hook lever by the nut screwed onto the stud for fastening the camshaft bearing housing.
We compress the valve springs with a cracker...
...and extract with tongs (or tweezers) crackers.
Weaken the springs.
Remove the valve cover...
...outer and inner springs,...
... as well as upper and lower spring support washers.
Using pliers, remove the oil seal from the valve guide.
In the absence of forceps, pry off the oil cap with two screwdrivers and remove it.
Attention! The operation is carried out carefully so as not to damage the fragile guide bushing.
Having lubricated the working edge of the new oil cap with engine oil, carefully put it on the valve stem.
Through the high head «at 12» or a mandrel, press the cap onto the valve guide.
We assemble the valve mechanism in reverse order. Remove the rod from the spark plug hole. After replacing the valve stem seals of the 1st and 4th cylinders, turn the crankshaft 180° (supporting the camshaft drive chain so that it is not pinched) and change the valve caps of the 2nd and 3rd cylinders.
We assemble the gas distribution mechanism in the reverse order. On a carburetor engine, we adjust the chain tension and thermal clearances in the valve drive.