Yangdong Co. Y90 Series Spezifikationen PDF herunterladen (Seite 23)

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Fig. 4 Tightening sequence

of

cylinder head bolts

SECTION

5.

CONSTRUCTION

OF

DIESEL

ENGINE

I .

Cylinder

Head

When

assembling,cylinder head is fixed

on

the

cylinder

block

with

cylinder

head

bolts.A

torsion

spanner

should

be

used during tightening the bolts.T'lle bolts are

tightened

several

times

in

sequence

shown

in Fig.4 until they

reach

the

specified

torque

Bmit.After

dismantling

and

asseJnbling

the

cvlinder

head.it is necessary

to

shut

down

the

engine

\vhen first

wanning up period

is

over.

Retighten

each

bolt

on

the

cylinder

head

according

to

the

specified

value

of

torque

J.hnit

and readjust

the

valve

lashes.

The

intake and

exhaust

valves

arc

made

of

different materials.Each

couple

of

the

valve

and

valve

seat

should

be

ground

in

order

to

prevent

leakage.

It is necessary to grind

\vhen gas leaks

out

due

to burning out'lmechanical pitting

and

"vear

appeared

on

the

sealing

face

of

valve

and

valve

seat.When

grinding'lapply a

grinding

paste(tlne

valve

sand)on

the

conic

[.;ealing surface

of

valve.l~hen

the valve

and

valve

seat

are

lapped

in

pair

unitJ

a

even.continuous

and

lustreless

sealing

band

appears.1t is strictly

forbidden

that

the

grinding paste enters

the

valve guide.After lapping.,clean

the

valve.valve

seat

and

valve

guide

carefulty.\Vearing

of

the

valve

guide

may

CC:l.use

the

eccentric

wear

of

valve

sealing

band

which

results in abnormal

sealing.Pour

sOlne

kerosene

or

diesel fuel into

the

gas passage'land

observe

\vhether there is

any

leakage.then

check

the valve sealing.

l~he

sealing

band

of

valve

and

valve seat is normally 1.2'-,·1.6

mIn

in

width

..

After a long

period

of

service

and

regrinding

many

tinlcs,the V\idth

of

v?lve

sealing

band

nlay

get

wider

..

vvhich

may

cause

abnormal

sealing.Being

kept concentrica!

\\.tith

respect

to

the

valve

guide hole'!

the

contact

band

on

valve seat is

to

be

refaced by a reanlcr.'Then

gring

the

valve

and

valve

seat

in pair.

5-1

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