MCi MC8 Crusader - Inst Alling Crankshaft; Pistons and Connecting Rods

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Crusader

MC-8

MAINTENANCE

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MANUAL

PIP

HARK

UP

WHEN

INSTALLED

ON

PISTON

GAP

II

0.005"

-,~

GRPOVE

Figure 4 - 6: Piston Fits & Tolerances

Used

unloader

mechanism

can be

replaced

by

unloader

kit

MCI

Part

No.

4C-

7-30.

The

new

unloader

pistons

should

be

a

loose

sliding

fit in

the

unloader

piston

bores

of

the

cylinder

block.

REPAIRS

DISCHARGE

VALVES

& SEATS:

If

discharge

valve

seats merely show signs

of

slight

wear,

they

can

be

dressed

by using a

lapping

stone,

grinding

com-

pound

and

grinding

tool.

Install

new

discharge

valves, valve springs,

and

cap

nuts.

The

discharge

valve

travel

should

be

between

.030"

and

.046"

To

test

for

leakage

by

the

discharge

valves

apply

about

I

00

pounds

of

air

pressure

through

the

cylin-

der

head

discharge

port

and

apply

soap

suds

at

the

discharge

valves

and

seats.

If

excessive leakage is

found,

leave

the

air

pressure

applied,

and

with the

use

of

a

fibre

or

hardwood

dowel

and

hammer,

tap the

discharge

valves

off

their

seats

several

times.

This

will

help

the

valves to

seat

and

should

reduce

any leakage.

With

air

pressure

still

applied

at

the

discharge

port

of

the

cylinder

head,

check

..

for

leakage

at

the

discharge

valve

cap

nuts.

No

leakage

is

permissible.

INLET

VAL

YES

AND

SEA

TS:

If

inlet

valve seats

show

sign

of

slight nicks

or

scratches,

they

can

be

redressed

with a fine

piece

of

emery

cloth

or

by lap-

ping

with

a lapping

stone,

grinding

compound

and

grinding

tool.

If

the seats

are

excessively

damaged

to

the

extent

that

they

cannot

be

reclaimed,

they

should

be

replaced.

The

dimension

from

the

top

of

the

cylin-

der

block

to the

inlet

valve

seat

should

not

exceed

0.145"

nor

be

less

than

0.101 ".

Slightly

worn

or

scratched

inlet valves

can

be

reclaimed

by

lapping

them

on

a

piece

of

fine

crocus

cloth

on

a flat surface,

but

it

is

suggested

that

new

inlet

valves be installed.

ASSEMBLY

INST

ALLING

CYLINDER

BLOCK:

Position

cylinder

block

gasket

and

bloc~

on

cra!1kcase ac-

cording

to

markings

made

pnor

to

d1sasse'!1bly.

Using

cap

screws

with

lockwashers,

secure

cylinder

block

to

crankcase.

INST

ALLING

CRANKSHAFT:

If

the

crankshaft

is

fitted with

oil

seal

rings,

install

rings.

Position

ball

bearings

and

crankshaft

in cr~nkca~~

making

sure

the

drive

end

of

the

crankshaft

1s

pos1t10ned as

marked

before

disassembly.

If

one

end

of

the

crankcase

is

counterbored

for

holding

a

bearing,

be

sure

the

crankshaft

is

installed

·

through

the

correct

end

of

the

crankcase.

-

Carefully

press

crankshaft

and

bearings

into

crank-

case using

arbor

press.

Position

a new

rear

end

cover

gasket

over

the

rear

end

of

the

crankcase

making

sure

the

oil

hole

in

the

gasket

lines

up

with

~he

~ii

hole

_in

t~e

crankcase.

Position

end

cover

with

011

seal

nng

mstalled

over

crankcase

and

end

cover

gasket.

The

end

cover

should

be

positioned

correctly

in

relation

to

the

oil

holes in

the

gasket

and

crankcase.

Secure

end

covet

to

crankcase

with

cap

screws

and

lockwashers.

If

the

opposite

end

cover

requires

an

oil

seal

which

was

removed

on

disassembly,

a

new

seal

should

be

pressed

into

end

cover.

Position

new

end

cover

gasket

and

carefully

install

end

cover

over

crankshaft

and

to

crankcase

avoiding

damage

to

the

seal.

Secure

end

cover

with

cap

screw

and

lockwashers.

PISTONS

AND

CONNECTING

RODS:

If

rods

are

steel,

they

can

be

re-used

and

serviced

as_

follow~.

However

it

is

recommended

that

the

alummum

die

cast

rods'

not

be

re-used

but

replaced

with

new

ones

when

re-building

compressor.

Do

not

~e-u~e

aluminum

die

cast

connecting

rods.

If

new

wnst

pm

bushings

are

to

be

used,

they sh_ould b~

pressed

i~to

the

connecting

rods

so

that

the

011

hole

m

the

bus~mg

lines

up

with

the

one

in

the

rod.

The

new

bushmgs

should

then

be

reamed

or

honed

to

provide

between

0.0001"

and

0.0006"

clearance

on

the

wrist

pin.

Position

connecting

rod

in

piston

and

press

in

wrist

pin

so

that

lockwire

hole

in th~

pin

aligns

wi_th

that

of

the

piston.

Install

new

lockw1re

t~rough

piston

_and

wrist

pin

and

lock

same

by

snappmg

~hort

end

mto

lockwire

hole

at

the

bottom

of

the

piston.

Install

piston

rings

in

correct

locatio~

_with

ring

pipmarks

up

(Figure

4-6).

Stagger

the

pos1t10n

of

the

ring

gaps.

Prelubricate

piston,

piston

rings,

~rist

I?in

and

c~n-

necting

rod

bearings

with

clean

engme

011

before

m-

stalling

them

in

the

compressor.

Remove

connecting

bolts

and

bearing

cap

from

one

connecting

rod.

Note:

It

is

important

that

caps

a~d

rods

are

not

intermixed.

Turn

crankshaft

so

one

of

its

connecting

rod

journals

is in ~he

downw~rd,

c~nter

position.

Insert

the

connectmg

rod

with

piston

through

the

top

of

the

cylinder.

whose

journal

is

down.

Position

and

attach

the

beanng

cap

to

the

con-

necting

rod

making

sure

the

bolt_

lockwashers

~re

properly

positioned

on

the

cap.

Tighten

connectmg

rod

bolts

evenly

and

bend

the

two

new

lockwasher

prongs

up

against

the

hex

h~ad

o~

the

bolt.

Install

the

other

connecting

rod

and

piston

m

the

same

manner.

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