Belarus 1221.2, Руководство оператора

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BELARUS-1221.2/1221 В .2/1221.3 Description and operation
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The
piston pin
is a hollow member made
of chrome-nickel steel. Pin axial displace-
ment in the piston-pin bosses is checked
by piston-pin retaining circlips.
The connecting rod is an I-section steel
part, with a bushing pressed into its top
end. To lubricate the piston pin, the con-
necting rod top end and the bushing are
provided with drilled passages. The bot-
tom end consists of the rod and cap which
bear the same markings. The connecting
rod caps are not interchangeable. Be-
sides, the connecting rods have group
designations of the mass of top and bot-
tom ends; these are marked on the end-
face of the top rod end. The engine shall
be fitted with connecting rods belonging to
the same group.
The main- and crankpin bearing inserts
of the crankshaft are thin-walled parts
made of bimetal strip. The shells are
manufactured in two sizes as to the inner
diameter, in accordance with the rated di-
ameter of the crankshaft necks.
The flywheel is made of cast iron and
bolted to the crankshaft flange. A steel
gear rim is pressed onto the flywheel.
The
valve actuating and timing gear (re-
fer to Fig. E-2) consists of timing gears,
camshaft, inlet and outlet valves, as well
as their fitting and driving parts.
The
camshaft
(1) is driven from the
crankshaft through the valve timing gears
and rides on four supports.
The tappets (2) are steel members, with
spherical bottoms. The camshaft cams are
made with a slight tilt that forces the tap-
pets to rotate when in operation.
The tappet pushrods (5) are made of a
steel bar. The downwardly concave part of
the tappet and cup the push-rod cup are
hardened.
The
valve rocker arms
(7) are made of
steel and rocks on rollers installed in sup-
ports. The rocker-arm roller is hollow, with
six radial bores for arm lubrication. Dis-
placement of the rocker arms along the
roller is restricted by spreader springs.
The inlet and outlet valves (3) are made
of high-temperature steel and free to
move in their guide bushes. The bushes
are press-fitted in the cylinder heads.
Each valve closes under the force of two
springs: outer (12) and inner (10) fixed on
its stem by means of a valve spring re-
tainer (9) and valve locating split cones
(10).
The sealing collars (18) fitted on the valve
guiding bushes keep oil from leaking down
into the engine cylinders through gaps be-
tween the valve stems and guiding
bushes.