SINGLE-CYLINDER ENGINES
Straight
edge
~
-=o
Feeler
--.....~
~
gauge
\..)
___
95
5
the
mea
surement with the specification in T
abl
e I.
If
gear back lash is incorrect, replace the
cam
sha ft
and crankshaft gears.
Bore
g
auge
faces.
Che
ck all core plugs for leaks
and
replace any that
are suspect. Sec
Core Plug Replacement in this chapter.
Check
oil lind coo lant passages for sludge, dirt and corro-
sion while cleaning. If the passages are very dirty , have
the block boi led out
by a machine shop.
Blowout
all pas-
sages
with compressed air.
Che
ck the threads in the head
bolt holes to
make
sure they arc clean. lf'dirty. use a tap to
restore the threads and r
emo
ve any
depo
sits.
2. Examine the block f
or
cracks To confirm suspicions
abou
t possible leakage areas. use a mixtu re
of
one
part
kerosene and tv..o parts engine oil. Coat the suspected area
with this solution. then wipe dry and immediately apply a
solution of zinc oxide disso lved in
wood
alcohol.
If
any
discoloration appears in the treated area. the block is
cracked and should
be replaced.
3. Check the flatness of the cylinder block deck or top
surface. Place an accurate
straightedge on the block. If
there is any gap between the block and straightedge, mea-
sure it with a flat feeler gauge
(
I-
"igurc 86). Measure from
end to end and from come r to c
om
er. Have the block re-
su
rf
aced if it is warped
mor
e than 0.07 mm (0.0028 in.).
4. Measure the cyl inder bore with a bore gauge (Fig ure
87) for out-of-rou ndness or excessive wear as
described in
Piston/Cylinder Bore Check in this chapter.
If
the cylin-
der
ex
ceed
s maximum tolerances. r
cbor
e the cylinder.
Rcbore the cylinder if the cy linder walls are badly
scuffed, scored or other
wise
damag
e.
CYLIl'IDER
BLO
CK
Cleaning and Inspection
I. Clean the block thoroughly with solvent. Remove any
gasket or RTV sealant residue from the machined sur-
Core
1)11l~
Replacem
ent
Check the condition
of
the front (Figure
HH
) and rear
(f igure H9)core plugs in the block whenever the engine is
out
of
the boat for
ser
vice. If any signs of leakage or corro-
sion arc found around one core plug. replace both
of
them .
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