Ill. Piston And Connecting-Rod - YANGDONG SERIES Y85 Operation & Maintenance Manual

to the camshaft bushes are slant.When dismantling and repairing the diesel engine,flush all lube
oil passages,and be sure that they are clean and unblocked.All passage plugs should be sp-aled
reliably and leakproof.
The main bearings are of complete suspension -support type.Since the mam bearing caps
and cylinder block are matched to bore,the matching marks are both on the bolck anu mam
bearing caps. Misplacement or inverted installation,when assem -bling,are prohibited.The mam
bearing shells are made of high-tin aluminium-base alloy. When dismantling for cleaning,be sure
that the upper and
Im~er
bearing shells are in right places(the upper shell with an oil groove).The
crankshaft thrust plates are assembled on the last main bearing with an upper piece and a lower
piece on each side.The thrust plates bear the axial force from the crankshaft.There are oil
channels on its operating surface which should be located against the thrust planes on the crank,
and its back surface is smooth.Never locate them in reverse.When tightening the main bearing
blots,two bolts on the bearing cap should be tightened several times in turn.Before tightening the
main bearing cap,strike the crankshaft forward and backward in order to keep the upper and
lower thrust plates in the same plane.Then tighten the bolts until they reach the specified
tightening torque.When completing the crankshaft assembly,turn it at the flywheel end by hand to
check whether it can be moved freely.
The liner is slipped into the cylinder bore yertically so that deformation of the liner may be avoided
The liner flange plane should protrude out the top plane of cylinder block by
o.07~.15mm
to keep an
excellant sealing between the cylinder liner and cylinder head,as shown in Fig6.
ill. Piston and Connecting-rod
The piston and connecting -rod assembly compnses the piston,piston rings,piston pm,
retaining rings,connecting -rod,connecting rod cap,connecting -rod bolts and connecting -rod
bearing shells and bush,etc. The mass difference of piston and connecting-rod assemblies in the
same engine should be within 20g.
All of the compression rings are made of alloy cast iron.The outer circle surface of the first
ring is plated with porous chrome in order to decrease the wear between the cylinder liner and
piston ring.The second ring has a conical surface.When assem-bling.the surface marked with a
sign"up"should be kept against the top of piston and be careful to avoid assembling in reverse.
The oil-control ring is of tensioning ring type.The radial force of oil ring is still kept while
decreasing the elasticity due to wear.Thus the service life of oil ring is prolonged.
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