Yaroslavl Engine Plant YMZ-536 Operation Manual page 75

The valves move in the guide bushings made of a sintered
material and press-fitted into the cylinder head. The intake valve
bushings have sealing collars.
1 – inlet valve; 2 – exhaust valve; 3 – stop ring; 4 – rocker arm shaft;
5 – exhaust valve rocker arm; 6 – intake valve rocker arm; 7 – rocker arm shaft
support; 8 – bolt securing supports; 9 – expansion spring; 10 - yokes
Yokes are made of hardened steel and are the same for the
intake and exhaust valves. The yokes are fixed on the valves by means
of a cylinder-shaped recess on one side and a groove on the other side,
ATTENTION! THE YOKES ARE INSTALLED ON THE VALVES
WITH THE CYLINDER-SHAPED RECESS FROM THE ROCKER ARM
SHAFT SIDE; REVERSE INSTALLATION IS INACCEPTABLE AS IT
WILL RESULT IN THE YOKE TOUCHING THE ROCKER ARM.
Valve springs are made of alloy steel wire, 3.9 mm in
diameter. The intake and exhaust valve springs are the same. Each
valve has one spring.
The spring bottom end thrusts against support washers installed
on the cylinder head; the top end thrusts against the spring cap fixed
on the valve stem with two split keys.
For the description of the valve train lubrication see
"Lubrication System" section.
Fig. 22. Valve train (top view),
located in the cylinder head:
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